Journal of
Clinical Medicine
Review
Biodistribution of Mesenchymal Stromal Cells after
Administration in Animal Models and Humans:
A Systematic Review
Manuel Sanchez-Diaz 1
, Maria I. Quiñones-Vico 2,*, Raquel Sanabria de la Torre 2, Trinidad Montero-Vílchez 1
,
Alvaro Sierra-Sánchez 2
, Alejandro Molina-Leyva 1
and Salvador Arias-Santiago 1,2,3
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Citation: Sanchez-Diaz, M.;
Quiñones-Vico, M.I.; Sanabria de la
Torre, R.; Montero-Vílchez, T.;
Sierra-Sánchez, A.; Molina-Leyva, A.;
Arias-Santiago, S. Biodistribution of
Mesenchymal Stromal Cells after
Administration in Animal Models
and Humans: A Systematic Review. J.
Clin. Med. 2021, 10, 2925. https://
doi.org/10.3390/jcm10132925
Academic Editor: Kyung-Rok Yu
Received: 12 May 2021
Accepted: 25 June 2021
Published: 29 June 2021
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conditions of the Creative Commons
Attribution (CC BY) license (https://
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4.0/).
1
Dermatology Department, Hospital Universitario Virgen de las Nieves, IBS Granada, 18014 Granada, Spain;
manolo.94.sanchez@gmail.com (M.S.-D.); tmonterov@gmail.com (T.M.-V.);
alejandromolinaleyva@gmail.com (A.M.-L.); salvadorarias@ugr.es (S.A.-S.)
2
Cellular Production Unit, Hospital Universitario Virgen de las Nieves, IBS Granada, 18014 Granada, Spain;
raquelsanabriadlt@gmail.com (R.S.d.l.T.); alvarosisan@gmail.com (A.S.-S.)
3
School of Medicine, University of Granada, 18014 Granada, Spain
*
Correspondence: maribelmqv20@gmail.com
Abstract: Mesenchymal Stromal Cells (MSCs) are of great interest in cellular therapy. Different routes
of administration of MSCs have been described both in pre-clinical and clinical reports. Knowledge
about the fate of the administered cells is critical for developing MSC-based therapies. The aim of this
review is to describe how MSCs are distributed after injection, using different administration routes
in animal models and humans. A literature search was performed in order to consider how MSCs
distribute after intravenous, intraarterial, intramuscular, intraarticular and intralesional injection
into both animal models and humans. Studies addressing the biodistribution of MSCs in “in vivo”
animal models and humans were included. After the search, 109 articles were included in the review.
Intravenous administration of MSCs is widely used; it leads to an initial accumulation of cells in the
lungs with later redistribution to the liver, spleen and kidneys. Intraarterial infusion bypasses the
lungs, so MSCs distribute widely throughout the rest of the body. Intramuscular, intraarticular and
intradermal administration lack systemic biodistribution. Injection into various specific organs is also
described. Biodistribution of MSCs in animal models and humans appears to be similar and depends
on the route of administration. More studies with standardized protocols of MSC administration
could be useful in order to make results homogeneous and more comparable.
Keywords: mesenchymal stromal cell; biodistribution; cell therapy
1. Introduction
Mesenchymal Stromal Cells (MSCs) are non-hematopoietic multipotent cells which can
be isolated from different tissues from adult, perinatal and fetal samples [1,2]. Some sources
are adipose tissue [3], bone marrow [4], umbilical cord Wharton’s jelly and blood [5,6],
periosteum [7], skin [8], amniotic fluid [9] and the placenta [10]. These cells have the
capability to differentiate into a variety of different mesenchymal lineage cells such as
osteoblasts, chondrocytes, adipocytes, fibroblasts and myoblasts [2].
Since MSCs have variable phenotypes, with different expression of bio-markers de-
pending on the source and means of isolation, as well as the tissue they come from, they
cannot be considered as a homogeneous set of cells [11]. The International Society for
Cellular Therapy set minimum criteria for characterizing human MSCs in order to pro-
mote a more uniform definition of MSCs. These criteria are: (a) Plastic adherence when
maintained in standard culture conditions; (b) Expression of CD105, CD73 and CD90
and lack of expression of CD45, CD34, CD14, or CD11b, CD79a or CD19 and HLA-DR
surface molecules; and (c) Differentiation into osteoblasts, adipocytes and chondroblasts
in vitro [12].
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MSCs are of great interest because of the possibility of using them as a part of ther-
apeutic regimens in a wide variety of human diseases, e.g., rheumatic and autoimmune
diseases, skin diseases and complex ulcers and wounds [13–16]. Some characteristics of
MSCs are fundamental for this purpose: (a) MSCs can be obtained from adult donors and
expanded in vitro without losing their immunomodulatory and differentiation potential;
(b) MSCs have hypo-immunogenic properties, so allogenic sets can be used, avoiding the
need for autologous cell cultures; (c) Their immunomodulatory and transdifferentiating
capabilities into different cell lineages can be exploited as a novel approach to the treatment
of different diseases [13–15,17–19].
Different routes of administration of MSC-based medical therapies have been de-
scribed both in pre-clinical and clinical reports, and the possible differences between them,
in terms of safety and efficacy, is an issue which is still under discussion [15,16,20–23].
These differences may be explained by the variable biodistribution of MSCs after their ad-
ministration. The most common reported routes of administration are topical, intravenous
and intraarterial, intramuscular and intralesional (including different locations e.g., skin,
spinal cord, tendons).
Given the presumable importance of the different mechanisms of MSC biodistribution
and their impact on the therapeutic effects, the objective of this systematic review is to
describe how MSCs are distributed after their inoculation through different administration
routes in animal models and humans.
2. Materials and Methods
2.1. Search Strategy
A literature search from January 2015 to April 2021 was performed using the Medline
database. The following search terms were used: MSC or MESENCHYMAL STEM CELL
or MESENCHYMAL STROMAL CELL or MULTIPOTENT STEM CELL or MULTIPOTENT
STROMAL CELL or STEM CELL AND BIODISTRIBUTION or DISTRIBUTION.
2.2. Inclusion and Exclusion Criteria
The search was limited to: (a) Human or animal data; (b) In vivo studies; (c) Studies
addressing the biodistribution of MSCs after any source of administration; (d) Articles
written in English or Spanish. All types of epidemiological studies (clinical trials, cohort
studies, case-control studies and cross-sectional studies) regarding the biodistribution of
MSCs were considered.
2.3. Study Selection
The titles and abstracts obtained in the first search were reviewed to assess relevant
studies. The full texts of all articles meeting the inclusion criteria were reviewed and their
bibliographic references were checked for additional sources. Articles considered relevant
were included in the analysis. Uncertainties about the inclusion or exclusion of articles
were subjected to discussion until a consensus was reached.
2.4. Research Questions and Variables Assessed
The research questions were as follows:
•
How do MSCs distribute after intravenous and intraarterial injection in animal models
and humans?
•
How do MSCs distribute after intramuscular injection in animal models and humans?
•
How do MSCs distribute after intralesional injection in different organs and tissues in
animal models and humans?
•
Which cell marking techniques have recently been used in studies on humans?
The variables assessed in order to answer these questions were the model which
received the MSCs (human or animal), the route of administration, the disease treated, the
cell-marking technique used, the biodistribution assessment method, the time when the
assessment was performed, and the outcomes regarding the biodistribution of the MSCs.
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3. Results
An initial search found 6808 references (see Figure 1). After reviewing the titles and
abstracts, 159 articles underwent full-text review. From this list, 50 articles were eventually
discarded due to various issues: 33 articles did not assess biodistribution; 7 were related
to other types of cells, rather than MSCs; 6 were not accessible or written in a different
language; 3 only addressed the issue of in vitro MSCs; and 1 article was duplicated. Finally,
109 studies met the eligible criteria and were included in the review.
Figure 1. Search strategy.
3.1. Biodistribution Characteristics of Mscs Depending on the Route of Administration
An overview and summary of all the information collected in this study can be seen
in Table 1.
3.1.1. MSC Biodistribution in Animal Models
First, the biodistribution of MSCs after their delivery or injection into animal models
will be discussed. Intravenous and intraarterial infusion, intramuscular injection and a
wide variety of intralesional administrations of MSCs will be addressed in this section.
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Table 1. Overview of the characteristics of each route of administration.
Route of
Administration
Systemic
Distribution
Organs to Which the Cells are
Distributed
Advantages
Disadvantages
Intravenous
Yes
First, cells move to the lungs
(first capillary filter).
Later, cells distribute, mainly to
the liver, spleen and kidneys.
Variable amounts of cells are
found in other organs.
Convenient route of
administration.
Widely used.
Useful to reach the
lungs.
Cells do not reach other
organs apart from
lungs in great
quantities.
Intraarterial (not
selective)
Yes
Cells bypass the pulmonary
filter so there is a wide
distribution in the rest of the
organs (heart, brain, kidneys,
liver, digestive system)
Convenient route of
administration.
Useful to bypass the
lungs and achieve
broader distribution.
Not so widely used.
Intraarterial infusion is
not common in clinical
practice
Intraarterial
(selective)
Yes (reduced)
Cells are distributed mainly in
the territory irrigated by the
cannulated artery. Distribution
of cells to other organs is
possible but in smaller amounts.
Targeted deposition of
cells is achieved.
Inconvenient route of
administration.
Difficult to transfer to
clinical practice
Intramuscular and
intraarticular
No
Cells remain at the injection site
Convenient route of
administration.
Targeted deposition of
cells is achieved
No systemic
distribution is
achieved.
Intradermal,
intratracheal,
intrapulmonary
and intraurinary
tissue
No
Cells remain at the injection site
Convenient route of
administration,
depending on each
specific route.
Targeted deposition of
cells is achieved
No systemic
distribution is
achieved.
Intrahepatic,
intrasplenic,
intrapericardial,
intramyocardial
Yes
Cells distribute following the
direction of the bloodstream
derived from the infused organ.
Targeted deposition is
achieved.
Knowledge about the
bloodstream derived
from the infused organ
might lead to targeted
distribution after
injection.
Inconvenient in clinical
practice.
Difficult to transfer to
clinical practice.
Injection into
cavities containing
body fluids
(peritoneum,
cerebral ventricles)
Yes (low
amounts)
Cells distribute mainly to tissues
in contact with the body fluid.
Convenient route of
administration,
depending on each
specific route.
Targeted deposition is
achieved.
Limited systemic
biodistribution.
Limited systemic
biodistribution.
Intrathecal
administration
No
Cells distribute caudally when
injected in the upper segments of
spine. Cranial migration of cells
after lumbar injection seems to
be possible if a high dose of
MSCs is administered (e.g.,
distribution to brain).
Convenient route of
administration if
deposition of the cells
at the central nervous
system level is desired.
Limited systemic
biodistribution.
Inconvenient in clinical
practice (depending on
the cases).
Intra-Central
Nervous System
Yes/No (variable
amounts)
Cells are able to distribute within
the central nervous system.
Factors leading to the movement
of the cells are still not clear.
Targeted deposition is
achieved.
Inconvenient route of
administration.
Difficult to transfer to
clinical practice.
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3.1.2. Distribution of MSCs after Intravenous Injection in Animal Models
Intravenous injection has emerged as the most widely used route in the various
research studies. This route of administration is a simple and effective way to deliver
MSCs systemically. Most of the studies discussed in this section agree on the general
characteristics of how mesenchymal cells are distributed after being injected into the
venous stream (Table 2, Figure 2). To begin with, some general ideas can be stated about
this issue: (a) after IV injection, most cells are retained initially in the lungs, which is
the first capillary filter; (b) there is later redistribution of the cells, mainly to the liver,
spleen and kidney, with few MSCs redistributing to other organs; (c) in some studies,
later redistribution is very limited; and (d) some pathological entities seem to alter this
biodistribution pattern.
A good example of this general distribution pattern can be seen in one study assessing
intravenous infusion of MSCs in a myocardial infarction model in dogs [24]. It showed high
distribution during the immediate post-infusion time in the lungs, with a posterior decrease
in the amount of MSCs and a later redistribution from day 1 to 7 in different tissues, mainly
in the liver, spleen and kidney. A similar model of myocardial infarction in mice [25]
showed early distribution in lungs but an insignificant amount of cells distributed to other
organs (less than 1%). Intravenous infusion of MSCs in baboons [26], and a late evaluation
of their distribution in a variety of tissues, have demonstrated a wide distribution of
MSCs after a long period of time: gastrointestinal, kidney, skin, lung, thymus, and liver
tissues contained MSCs. Similar results were shown in several other studies [27–31]. The
redistribution might be explained by phagocitation of MSCs: monocytes might perform
this action, and then change their immunophenotype, inducing Treg cells [32].
Figure 2. Biodistribution of MSCs after intravenous infusion. After intravenous infusion, there is initial biodistribution in
the lungs. Later, most cells redistribute to the liver, kidney and spleen. Few cells can be found in other organs and tissues.
In some cases, diseased tissues have been found to be capable of attracting MSCs.
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The alteration of the general distribution pattern in specific diseases has also been
reported in several studies. Zhang et al. [33] found a significant amount of MSCs in the
kidneys of rabbits with acute kidney injury. Similar results have been shown in a model of
Alzheimer’s disease [34,35] with higher brain distribution of MSCs in diseased animals
compared to healthy animals. This was also evidenced in another study performed on
mice with cerebral tumors [36], rats and beagle dogs with spinal cord injury [37,38], and
rats with intracerebral hemorrhage [39]. Moreover, acute distress respiratory syndrome or
liver tumors may also affect the distribution of cells after intravenous injection [40,41]. In
contrast, in a murine model of experimental autoimmune encephalomyelitis [42], MSCs
were not distributed to the brain area.
Although the lungs seem to be the area MSCs mostly distribute to after intravenous
injection, Schmuck et al. [43] concluded that this may be due to the lack of sensitivity of
bioluminescence techniques, which are carried out in most biodistribution studies. In their
study, which used a 3D cryo-imaging system, they demonstrated a higher concentration of
MSCs in the liver when compared to the lungs after intravenous infusion in rats with acute
lung injury. In this line, Schubert et al. [44] demonstrated a high distribution of MSCs to
the lungs with bioluminescence techniques on day 1 after intravenous infusion in mice
with acute kidney injury. Cells cleared on days 3 and 6. However, when RT-PCR was
performed on several tissues on day 6, variable amounts of mRNA were detected in the
blood, liver, kidneys and lungs. Therefore, RT-PCR could be a better option for detecting
the late presence of MSCs in tissues and could be used to complement imaging techniques.
Other situations, such as the modification of MSCs or the selective infusion of MSCs
into certain veins, might also affect biodistribution. Moreover, some studies have shown
that modifying MSCs may lead to cells selectively targeting specific organs. The modifi-
cation of specific “homing markers” or adhesion molecules can lead to targeted homing
of MSCs. This has been proven by modifying MSCs to achieve specific distribution to
the liver [30]. In addition, the selective intravenous delivery could lead to differences in
biodistribution. For example, Li et al. [45] demonstrated that superior mesenteric vein
infusion of MSCs leads to more selective and longer homing of MSCs in a model of acute
liver injury when compared to intravenous and inferior vena cava delivery.
Finally, regardless of the source of administration, Fabian et al. [46] demonstrated that
the age of both the recipient and the donor of MSCs seems to affect the biodistribution of
the cells. The study demonstrated that old recipients and donors showed a very restricted
biodistribution of MSCs in mice after 28 days (mainly in the brain cortex and spleen)
whereas young receptors and donors showed a wide variety of distribution.
3.1.3. Distribution of MSCs after Intraarterial Injection in Animal Models
Intraarterial infusion of MSCs has been used as an alternative and has also been
compared to IV injection in several situations (Table 3, Figure 3). Briefly, the main charac-
teristics of this route of administration are: (a) IA injection bypasses the pulmonary filter,
so low amounts of MSCs are retained in these organs; (b) MSCs distribute more widely
into the rest of the body’s organs after IA infusion compared to IV delivery; (c) like the IV
route, biodistribution after IA injection might be modified by several diseases; d) selective
intraarterial delivery of MSCs might be very useful for targeting diseased organs.
As an initial example of these characteristics, one study performed on pigs [22]
compared intravenous and intraarterial infusion techniques. MSCs were detected using
SPECT/TC imaging, which showed a lower pulmonary captation in the intraarterial group,
and a relatively higher uptake in other organs such as the liver, spleen and kidney. This
was also studied in an acute kidney injury model in mice [47]. In this study, a significantly
higher amount of MSCs were detected in the kidneys after intraarterial infusion, especially
in mice with AKI. In contrast, the vast majority of MSCs were distributed to the lungs
after intravenous injection. Moreover, intracardiac injection has also been reported to be an
effective delivery route. This route of administration can be considered to be equivalent
to the IA route when the cells are injected into the left chambers of the heart. In fact, after
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intracardiac injection [48], MSCs seem to follow a similar path; widespread distribution is
observed (lungs, brain, spleen, liver, kidneys).
The fact that the IA route leads to a significantly higher distribution of MSCs in
peripheral organs might be an interesting characteristic when homing MSCs in the diseased
area is desirable. For example, in other studies it has been proven that intraarterial injection
improves distribution to the damaged cerebral areas when compared to intravenous
injection [49–51].
Regarding the distribution of MSCs to the brain after intraarterial infusion, Cerri
et al. [52] evaluated distribution to the brain of MSCs injected in the carotid artery of a
Parkinson’s disease murine model. One group was treated with mannitol as a transient
permeabilizing factor of the blood-brain barrier. Later assessment showed that rats not
treated with mannitol had an extremely low amount of MSCs homing to the brain, whereas
the group treated with mannitol showed a significantly higher amount of MSCs. Moreover,
most of the cells were distributed in the ipsilateral hemisphere to the carotid used to inject
them. Therefore, the use of a permeabilizing agent could be essential to allow the passage
of MSCs into the brain. On the other hand, selective delivery of cells might help MSCs
reach the damaged areas [51,53].
Figure 3. Biodistribution of MSCs after intraarterial infusion. When cells are administered into a peripheral artery, the lungs
are bypassed and a wide distribution of cells is found in organs and tissues. Selective intraarterial delivery of cells targets
the distribution of cells to organs which are irrigated by the cannulated artery.
As occurred with IV injection, some pathological entities can modify the biodistri-
bution of MSCs after IA injection. In the specific case of mice with inflammatory bowel
disease, MSCs do not significantly distribute to lungs or liver but distribute mainly to
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the affected areas of the intestine [54]. In contrast, in a model of kidney injury, MSCs did
not distribute to damaged kidneys after intracardiac injection [55]. Moreover, the dose of
MSCs seems to be important when administered IA. One study showed that an increased
dose of IA-administered MSCs led to a wider distribution of cells but also to a high degree
of intravascular cell aggregation and mortality [56]. Thus, the dose of MSCs should be
assessed before intraarterial delivery to avoid intraarterial aggregation.
The homing of MSCs to diseased tissues can be improved by selective intraarterial
infusion. With this technique, MSCs are directly injected into selected arteries. This results
in a greater amount of MSCs in the targeted organs. Some examples are discussed here:
When MSCs are delivered directly into the renal artery, MSCs seem to distribute only in
the kidneys, without systemic significant distribution, and mainly in the renal cortex [57].
Therefore, renal intraarterial MSC infusion limits off-target engraftment, leading to efficient
MSC delivery to the kidneys. Similar results were found after selective intraarterial infusion
into the superior mesenteric artery regarding the intestine distribution of MSCs [58], and
the selective intraarterial limb infusion [59,60], with MSCs distributed in the target area
and a small quantity of MSCs in the rest of the organs.
3.1.4. Distribution of MSCs after Intramuscular Injection in Animal Models
As this is widely used with classic drugs, intramuscular injection of MSCs has also
been studied as a possible way to administrate MSCs (Table 4, Figure 4). As a general
idea, whereas intramuscular injection of conventional drugs leads to a significant systemic
distribution, MSCs injected intramuscularly do not seem to distribute to the rest of the body.
One study performed on mice to assess the sensitivity and specificity of quantitative
PCR [61] for detecting MSCs showed that, 3 months after intramuscular injection of MSCs,
no MSCs were detectable in any internal organ. However, DNA from MSCs was still present
in the muscles where it was injected. This could suggest that MSCs do not distribute to other
organs after intramuscular injection. This was in line with the findings of similar studies
performed following intramuscular injection [62–64], with MSCs remaining at the injection
site, but without MSCs distributing to organs. However, it has been demonstrated that,
despite the lack of distribution of MSCs, when injected intramuscularly in a contralateral
muscle to an inflamed area, MSCs are capable of reducing inflammation. This is thought to
be performed by the release of soluble factors rather than the movement of the cells [65].
A recent review of intramuscular MSCs showed that, to date, no articles have found
significant systemic biodistribution after intramuscular injection of MSCs [65].
3.1.5. Distribution of MSCs after Intralesional Injection in Animal Models
Several different intralesional routes of administration for MSC delivery have been
described. The most important routes of administration of MSCs into lesioned areas will
now be addressed
•
Intraarticular (IAr) delivery of MSCs (Table 4, Figure 4):
Intraarticular injection of MSCs has been widely studied in different animal models.
As a general idea, IAr injection lacks systemic biodistribution, whereas it leads to a very
targeted delivery of cells into the joints. This has been adequately demonstrated by studies
on different mice models of healthy animals, arthritis and osteoarthritis, where it was shown
that MSCs do not distribute to other organs following intraarticular injection [21,66–69].
Markides et al. [70] assessed the biodistribution of MSCs in a sheep model of osteochondral
injury. After intraarticular injection, MSCs were only detected in the synovium, with a
lack of MSCs within the chondral defect. Khan et al. [71] showed similar results after
intratendinous injection, with no MSCs spreading from the injection site.
In contrast with that already described, some studies show an incidental distribution
of MSCs. In these cases, MSCs have been shown to be present in the blood, distant zones
or tendon lesions near the injection site. One study performed on a horse model of tendon
lesions [72] showed that, although the vast majority of cells remained at the site where they
had been injected, a small amount of MSCs could be found in blood for the first 24 h after
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injection, as well as in the contralateral control tendon lesions which had not been injected.
Similar results were observed by Shim et al. [73]; after intraarticular injection, MSCs were
detectable in blood with a peak at 8 h. No systemic distribution was observed. Moreover,
other studies show that MSCs seem to be able to migrate from the joint to nearby tendinous
lesions [74,75].
Figure 4. Biodistribution of MSCs after intraarticular and intramuscular injection. No systemic distribution has been
demonstrated after intramuscular or intraarticular injection. After intraarticular injection, MSCs have been found to be able
to migrate to nearby damaged lesions and into the bloodstream. Moreover, the use of a magnet on MSCs with a magnetic
label is useful for targeted deposition of cells within the joint.
As occurred with the IV and IA routes, elective accumulation of MSCs in selected areas
of a joint (i.e., a chondral lesion within the joint) can be achieved. MSCs must be modified
by magnetic labeling. The subsequent use of a magnet during the transplantation [76] leads
to the movement of the cells within the joint so they can be deposited in the target zone.
Finally, as a variant of IAr delivery, one study was performed to assess biodistribution
of MSCs which were pre-loaded into bone grafts [77]. This study also showed the lack of
systemic biodistribution of MSCs and the long-lasting MSCs in the graft up to 6 weeks.
Similar results were found when injecting MSCs into the femoral head of pigs [78].
3.1.6. Injection of MSCs into the Reproductive and Urinary System
Some studies have been found on the issue of biodistribution of MSCs after injection
into the urinary and reproductive systems. In a rat model of birth-trauma injury [79], the
presence of MSCs following local injection into the periurethral tissues was demonstrated
up to 7 days post-injection. In this case, no tests were performed to assess the distribution
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to other organs after local injection. Ryu et al. [80] injected MSCs into the outer layer of the
bladder in a interstitial cystitis model. It was demonstrated that cells are able to migrate
from the outer layers of the bladder to the urothelium for the first 30 days after injection
and to home as perivascular cells. Dou et al. [81] found that after intracavernous injection,
MSCs distributed to the lower abdomen in a erectile dysfunction model in mice in the first
hour. Moreover, MSCs can be found in kidney, prostate and hepatic tissues up to 7 days
after injection. Finally, when injected into the ovaries, MSCs are able to distribute to the
uterus, with no systemic distribution Table 5 [82].
3.1.7. Injection of MSCs into the Central Nervous System
There is a wide variety of reports concerning the injection of MSCs into the central
nervous system Table 6: Intrathecal, intracerebral and intraventricular injections have been
described:
(a)
Intrathecal injection of MSCs: After intrathecal injection, Barberini et al. [83] demon-
strated that MSCs do not seem to distribute cranially (when injected in the lumbosacral
area), whereas they can progress caudally (when injected in the altanto-occipital area).
In this study, no MSC engraftment was demonstrated. The systemic biodistribution
of the MSCs was not specifically assessed, but imaging techniques did not show
the presence of MSCs in areas other than the central nervous system. In contrast,
Kim et al. [84] demonstrated that MSC migration from the spine to the brain is pos-
sible in a dose-dependent manner. Quesada et al. [85] also demonstrated brain
migration after intrathecal injection;
(b)
Intracerebral injection of MSCs: Wang et al. [86] demonstrated that intracerebrally
injected MSCs loaded with paclitaxel are capable of spreading from one cerebral
hemisphere to another in a glioma model in mice in two days. These cells were found
to spread from the healthy hemisphere to the glioma hemisphere and to invade the
tumor. The ability of MSCs to migrate from one hemisphere to another has also
been demonstrated in other studies [87]. In other reports [88–93], MSCs injected
intracerebrally were detectable at the site of administration 1–3 weeks after injection,
with a subsequent rapid decrease and no significant systemic distribution. Other
studies [94] showed that MSCs can be detected with fluorescence and bioluminescence
up to 7 weeks after transplantation;
(c)
Intraventricular injection of MSCs: Some studies showed that MSCs injected into
cerebral ventricles are able to migrate to large blood vessels in a brain traumatic injury
model [95], and also to brain parenchyma and the spinal cord [96]. In contrast, other
reports [97] demonstrate that after intraventricular infusion, MSCs do not migrate
to brain parenchyma and are hardly able to migrate to the spinal cord in a model of
amyotrophic lateral sclerosis.
Finally, one review showed that intranasal delivery of MSCs led to significant intrac-
erebral migration of MSCs [98].
3.1.8. Injection of MSCs into the Digestive System:
(a)
Intrahepatic and intrasplenic injections have been studied in several reports as efficient
delivery routes for administrating MSCs. After intrahepatic injection, Xie et al. [99]
demonstrated that MSCs remain in the liver and are cleared in a short period of time,
without systemic distribution. This short period of time might be in association with
NK cell activation: Liu et al. [100] showed that mice with activated NK cells had a
more rapid clearance of intrahepatic MSCs. Yaochite et al. [101] injected MSCs into
the liver and spleen of diabetic mice. It was shown that intrasplenic MSCs were able
to move to the liver whereas intrapancreatic cells remained at the site of the injection.
No systemic distribution was shown and cells remained for up to 8 days. Similar
results were found in another study [102], with MSCs remaining for up to 4 weeks;
(b)
When injected intraperitoneally [103,104], MSCs seem to spread mostly to abdominal
organs (liver, spleen and intestine) with little distribution to the lungs, heart, blood
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and lymph nodes. Other study shows that Wharton’s Jelly MSCs are capable of
distributing to the whole body after intraperitoneal injection at days 1, 7, 14 and 21 in
piglets [105].
(c)
When injected in the peri-fistula area [106], MSCs do not seem to distribute systemically.
3.1.9. Injection of MSCs into the Cardiovascular and Respiratory Systems
Some articles have addressed the injection of MSCs into the pericardium or the my-
ocardium. When injected intrapericardially [107] in a myocardial infarction model, MSCs
seem to distribute to ventricles and atriums, with a preference for the left ventricle. Regard-
ing intramyocardial injection, MSCs seem to distribute initially in the myocardium, with
posterior redistribution to the lungs, liver and bone [108]. Moreover, it has been demon-
strated that after intramyocardial injection, if a repeated ischemia model is performed,
MSCs tend to home mainly to the heart with less distribution to peripheral organs [109]. Fi-
nally, some studies were related to the injection of MSCs into the respiratory system: When
injected intratracheally or intrabronchially, MSCs do not distribute systemically [110,111].
3.1.10. Injection into the Skin, Subcutaneous Cellular Tissues and Lymph Nodes
Few studies have addressed the issue of biodistribution after intradermal injection of
cells (Table 5). When injected into the skin of mice, Tappenbeck et al. [112] demonstrated
that MSCs seem to remain in the skin and migrate to lymph nodes, without significant
systemic distribution. Regarding the specific distribution in cutaneous wounds [113,114],
MSCs seem to distribute with a diffuse pattern initially and later concentrate towards the
wound edges. Finally, these cells seem to be engrafted with the newly developed skin
tissue. No systemic distribution following intradermal injection had been reported. Only
one study was performed to describe biodistribution after intranodal injection; in this
study, most MSCs remain at the injection site or in the fat surrounding the injected nodes
48 h later [103], without systemic distribution of cells.
3.2. Biodistribution of MSCs in Humans
Only a few reports of the biodistribution of MSCs after the injection into human
models have been recorded in this review (Table 7). These articles will be discussed in the
following sections.
3.2.1. Distribution of MSCs after Intravenous Injection in Humans
Three studies regarding the intravenous injection of MSCs into humans were identified
in order to assess biodistribution. In the first study, the intravenous infusion of MSCs in
patients suffering from cirrhosis showed an early (pre-48 h) distribution mainly in the
lungs, with a later decrease in lung captation and a high distribution in the spleen and
liver [115]. In another study on breast cancer patients, MSCs were monitored in peripheral
blood after intravenous injection [116], finding a rapid clearance of MSCs in blood, with
no cells detected 1 h post injection. Finally, a third article showed that when injected
intravenously into a patient with hemophilia A [117], MSCs distributed early to the lungs
and liver, with a progressive decrease. Distribution to the usual bleeding places was shown
at 24 h.
As can be seen, biodistribution after IV injection in humans seems to be similar to
that described in animal models: (a) early captation in the lungs; (b) later distribution in
organs such as the spleen and liver; and (c) distribution of MSCs into target areas have
been described.
3.2.2. Distribution of MSCs after Intraarterial Injection in Humans
Only one study addressed the intraarterial infusion of MSCs in humans. This study
was performed on 21 type 2 diabetes mellitus patients. MSCs were selectively injected
intravenously or intraarterially (into the pancreaticoduodenal artery and the splenic artery).
MSCs were labeled with 18-FDG and PET-TC images were used to assess biodistribution.
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Selective intraarterial delivery led to MSCs homing to the pancreas head (when cells
were injected into the pancreaticoduodenal artery) or body (when infused into the splenic
artery); whereas no MSCs were found in the pancreas in the intravenous group. This report
shows that biodistribution after IA infusion of MSCs seem to be similar to biodistribution
in animal models, with systemic delivery, a lack of lung trapping and the possibility of
selective infusion into certain areas.
3.2.3. Distribution of MSCs after Intralesional Injection in Humans
Only one study of intralesional injection of MSCs and their biodistribution was ob-
served. Henriksson et al. [118] injected MSCs into intervertebral discs in 4 patients. Discs
were explanted at 8 and 28 months post injection. Histologic examinations found the pres-
ence of MSCs in intervertebral discs after 8 months, with chondrocyte-like differentiation.
No cells were found in the discs after 28 months, and no systemic distribution was assessed.
3.2.4. Distribution of MSCs after Intracoronary Injection in Humans
In one study, biodistribution of MSCs after intracoronary injection was assessed.
Lezaic et al. [119] injected MSCs into the coronary arteries of 35 patients with idiopathic di-
lated cardiomyopathy. They showed that a very low number (0–1.25%) of MSCs are retained
in the myocardium, with the majority distributed to the liver, spleen and bone marrow.
3.2.5. Which Cell-Marking Techniques Have Recently Been Used in Preclinical Studies?
A wide variety of cell-marking techniques have been used for preclinical studies
involving cell therapy. Also, a wide variety of detection methods have been performed.
Since it is not the objective of this review to address these techniques in depth, an overview
of them is reviewed hereafter.
Most common cell-marking techniques can be divided into: (a) those related to the use
of radionuclides; (b) those related to bioluminescence imaging systems; (c) those related to
the use of magnetic resonance imaging (MRI); and (d) those related to the genetic marking
of cells.
The use of radionuclides is a common technique which is useful to assess the distribu-
tion of previously marked cells in preclinical models. Some of the most common radionu-
clides include 99mTechnetium-hexamethylpropyleneamine oxime (9mTc-HMPAO) [21,83],
or 111Indium-Oxine (111In-Oxine) [60,115]. After culture, these substances enter into the
cells. Once the cells are administered, the emitted radioactivity can be detected by imaging
techniques such as Single Photon Emission Computed Tomography (SPECT) or Positron
Emission Tomography (PET), which allow us to track the fate of the cells. The main dis-
advantage of these methods are the limited duration of the radioactivity, which limits the
assessment of the late distribution of cells, and the dangers related to the management of
radioactive substances in the laboratory.
Bioluminescence imaging systems are based on the light which is emitted by cells
which have been previously transfected with the firefly luciferase gene (luc gene) [99,100].
Once the cells transfected with this gene are administered to the animal, an injection of D-
luciferin is performed. After D-luciferin has been administered, cells containing the specific
gene fluoresce, emit light with a wavelength of 537 nm. This light can be detected by
specific imaging systems to assess biodistribution. The main disadvantage of this method
is that bioluminescence has limited spatial resolution and reduced tissue penetration due
to the relatively weak energy of emitted photons. For these reasons, its use in large animal
models is not advisable [120].
The use of superparamagnetic iron oxide nanoparticles (SPIONs) is also a useful
technique to assess cell biodistribution. SPIONs are small synthetic iron particles which
are coated with certain biocompatible polymers. When cells have been labeled with these
particles, they are detectable by imaging techniques such as MRI techniques [121]. Given
that magnetic resonance imaging is a technique that is not very accessible, the use of this
method can be limited.
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Finally, it is possible to label cells with specific genes that can be subsequently detected
by PCR methods [26,44,105]. The main disadvantage of this cell-marking technique is that
a tissue sample is required so that the distribution of cells cannot be assessed in vivo in
most cases.
3.2.6. Which Cell-Marking Techniques Have Recently Been Used in Studies with Humans?
The studies included in this review used different cell-marking techniques. The most
common techniques are those related to the use of a radioactive labeling: MSCs can be la-
beled with radionuclides in vitro, and then injected into humans. Radionuclides used in the
reviewed articles include 111Indium-Oxine (111In-Oxine) [115,117], 18-Fluorodeoxyglucose
(18F-FDG) [122] and 99mTechnetium-hexamethylpropyleneamine oxime (9mTc-HMPAO) [119].
Cells are incubated in culture mediums containing these substances, which enter into the
cells. Later assessment of the emitted radioactivity of these substances in the body with
imaging techniques such as scintigraphy, Single Photon Emission Computed Tomogra-
phy (SPECT) or Positron Emission Tomography (PET) allow us to detect the distribution
of the cells in the body to be evaluated. The main disadvantage of radionuclide-based
cell-marking techniques is the limited duration of the radioactivity; as the radionuclides dis-
integrate, the emitted signal becomes smaller and finally disappears, making it impossible
to evaluate the late biodistribution of the cells administered.
Labeling cells with markers which can be detected in histologic samples is another
technique used in humans. In the study reviewed [118], iron sucrose was used to label
cells. This compound makes cells detectable in histologic samples. The main advantage of
this kind of marker is its presumably long duration (longer than radionuclides). However,
the use of histologic markers makes it necessary to perform ex vivo examination which
is a limiting factor for its use in humans. The use of flow cytometry [116] to evaluate
cell markers could be considered to be comparable to the use of histologic markers, and
involves the extraction of biologic samples to evaluate cell distribution.
4. Discussion
Determining the fate of MSCs after administration is a major issue in the development
of cell therapies. On one hand, as a part of their physiological functions, MSCs are able
to produce several soluble substances and to modulate the immune response through
different pathways; the production and induction of interleukin production and the release
of microvesicles [123–125]. Cell interactions lead to the secretion of soluble factors and
cell-to-cell contact which induces changes in the immunobiology of immune cells, such as
changing the interleukin production, inducing anergy or triggering apoptosis. On the other
hand, MSCs have been found to be able to differentiate into different cellular subtypes,
which could play a role in regenerative medicine. Whether MSCs act by modulating the
immune system or differentiating into tissular cells, understanding how and where cells
are distributed after being administered by each route of administration is critical.
Intravenous injection of MSCs remains the most widely used form of administration.
The widespread use of this route of administration for drugs which are used in clinical
practice, and the ease of administering cells by this route, are probably the reasons why.
As previously seen, IV administration might be beneficial when cell trapping in the lungs,
liver or spleen is pursued, or when MSCs are capable of acting at a distance. However,
intraarterial delivery might be of choice when wide systemic distribution into different
tissues and organs is required. Moreover, if a targeted deposition of cells into a single
organ is needed, intraarterial selective delivery could be the solution. In contrast to
intravascular administration, intramuscular injection seems to lack significant systemic
distribution of cells and might be preferred when the cells do not necessarily need to reach
the target tissues.
Regarding intralesional administration of MSCs, there are several distribution patterns
depending on the organ or tissue injected. Intraarticularly injected MSCs seem to remain
in the joints, which could be of benefit when treating articular diseases. Administration
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into skin, lymph nodes, trachea, lungs and urinary tissues does not produce systemic
distribution either, and might be useful when targeted delivery is required. In contrast,
intrahepatic, intrasplenic, intracardiac and intrapericardial infusion led to a distribution of
MSCs following the natural direction of the bloodstream. Moreover, the injection of cells
into virtual anatomical cavities containing corporal fluids seems to produce a distribution
of MSCs within the same anatomic areas: intraperitoneal, intra-cerebro-ventricular and
intrathecal routes of administration make MSCs reach the organs and tissues in contact
with the correspondent fluid. Finally, intracerebrally administered MSCs are able to move
within the brain if induced to do so by appropriate stimuli.
5. Limitations and Future Studies
Although the fate of MSCs after each route of administration seems to be fairly well
understood, the specific mechanisms which lead to these distribution patterns are still a
matter of discussion. Moreover, as has been previously reviewed [30,46], these mechanisms
might be modulated by specific factors such as the surface molecules expressed by MSCs
or the age of the donors and recipients of cells. Although this is still unknown, other
factors, such as the specific subtype of MSC or the donor and recipient model, could also be
important. Moreover, there is great variability among different studies with respect to the
exact forms of administration (e.g., the exact anatomical site injected or the concentration
or volume of cells administered). The design of standardized protocols for mesenchymal
cell administration could lead to less variability of results, making them more comparable.
6. Conclusions
Biodistribution of MSCs in animal models and humans appears to be comparable. In
response to the research questions, some facts are worth noting:
(a)
Intravenous administration leads to an initial accumulation of cells in the lung with
later redistribution to the liver, spleen and kidneys;
(b)
Intraarterial injection bypasses the pulmonary filter, so MSCs distribute more widely
into the rest of the organs of the body;
(c)
In both of the two previous routes of administration, selective perfusion of selected
blood vessels is useful for targeting specific organs;
(d)
MSCs are not distributed systemically in significant quantities after intramuscular,
intraarticular, intradermal, intranodal, intratracheal, intrapulmonary and intraurinary
tissue administration;
(e)
The injection into specific organs, such as the liver, spleen, pericardium or heart leads
to a distribution of MSCs following the direction of the natural bloodstream;
(f)
The injection into anatomical cavities containing body fluids (cerebral ventricles,
subarachnoid space and peritoneum) leads to a distribution of MSCs in tissues which
are in contact with the fluid;
(g)
MSCs injected intracerebrally seem to be able to migrate within the central ner-
vous system.
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Table 2. Biodistribution after IV administration of MSCs in animal models.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Krueger et al.
[126] (2018)
Adult
baboons [26]
Lethal total body
irradiation
(3 animals)
Intravenous
(autogenic and
allogenic MSCs)
Genetic transduction with green
fluorescent protein retroviral
construct, which was later
evaluated by PCR.
Necropsies were performed between 9 and
21 months following MSC infusion.
Several tissues were found to have MSCs:
Gastrointestinal, kidney, skin, lung,
thymus, and liver.
Gastrointestinal tissues had
the highest MSCs
concentration.
MSCs distribute to a wide
variety of tissues following
systemic administration.
Mongrel dogs
[24]
Miocardial infarction
(7 animals)
Intravenous
(allogenic MSCs)
111In oxine–labeled MSCs
colabeled with
ferumoxides–poly-l-lysine.
Single-photon emission CT
(SPECT) and x-ray CT
(SPECT/CT) and MRI studies
were used to evaluate the
distribution.
Imaging was performed immediately after
injection and at multiple time points
between 1 and 7 days after infusion.
Early imaging showed a high distribution
to lungs, which later decreased drastically.
After day 1, MSCs distributed from lungs
to different organs (kidney, bone marrow,
liver, spleen) and also to the infarcted area.
A high and early
distribution to lungs is
showed, with a progressive
decrease of MSCs and a later
redistribution to a wide
variety of tissues.
Mice [25]
Miocardial infarction
(number unknown)
Intravenous
(xenogenic
MSCs—human
MSCs)
Human MSCs were infused,
Quantitative assays for human
DNA and mRNA were used to
evaluate the distribution,
Tests were done at 15 min, and up to 100 h
post infusion.
Early distribution to the lungs was detected
(15 min).
Later distribution to other organs was
insignificant: less than 1% of cells was
detected in any other organ after 48 h.
Authors conclude that
effects of intravenous MSCs
might be due to soluble
mediators rather than
engraftment of MSCs in
target tissues.
Mello et al.
[39] (2020)
Rats
Intracerebral
hemorrhage
Intravenous
(xenogenic
MSCs—human
MSCs)
99mTc was used to label MSCs.
Scintigraphy and radioactivity
measurements (cerebral
hemispheres, heart, lungs, liver,
kidneys, intestines, and spleen)
were performed to assess
biodistribution.
Scintigraphy was performed 2 h after cell
injection and ex vivo radioactivity was
evaluated 24 h after cell transplantation.
MSCs were mainly distributed to the lungs,
kidneys, spleen and liver. Brain captation
was low but it was relatively higher in the
damaged hemisphere.
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Patrick et al.
[127] (2020)
Mice
Lung cancer
Intravenous
(xenogenic
MSCs—human
MSCs)
89Zr-oxine and luciferase were
used to label MSCs. PET-CT,
bioluminescence and ex vivo
radioactivity measures were
used to assess biodistribution.
PET-CT at 1 h and 1, 2, and 7 days
post-injection. At 7 days, radioactivity was
measured from ex vivo organs.
The majority of signal (60%) was found in
the lung at 1 h before decreasing, while
liver signal increased. From 1 to 7 days
post-injection, the proportion of the 89Zr
signal in the lung fell further from 24.6%.
Wuttisarnwattana
et al. [128]
(2020)
Mice
Bone marrow
transplanted animals
Intravenous
(xenogenic
MSCs—human
MSCs)
Red quantum dots were used to
label MSCs. Ex vivo
cryo-imaging was performed to
assess biodistribution in
different tissues (lung, liver,
spleen, kidneys, bone marrow).
Animal sacrifice was performed at different
time points following stem cell infusion (24,
48, 72 h).
Initially, MSCs were found as clusters in the
lung and eventually dissociated to single
cells and redistributed to other organs
within 72 h, mainly to the spleen and liver.
De White
et al. [32]
(2018)
Mice
Healthy animals
(number unknown)
Intravenous
(xenogenic
MSCs—human
MSCs)
Qtracker 605 beads and
Hoechst33342, which labelled
alive and dead cells, respectively.
Anatomical and molecular
fluorescence videos were
generated with CryoViz
Technology.
Blood tests were performed to
analyze phagocytosis.
Necropsies were performed at 5 min, 24 h
and 72 h post-infusion.
Early accumulation of MSCs in the lungs
(5 min) was demonstrated. MSCs were
phagocytized in the lungs and redistributed
to liver within the monocytes at 24 and 72 h.
Monocytes change their immunophenotype
after phagocyting MSCs, and induce Treg
cells.
Authors conclude that the
action of MSCs in many
organs may be due to the
phagocytosis of MSCs by
monocytes and the later
change in their phenotype,
which leads to the induction
of Treg cells.
Ehrhart et al.
[35] (2016)
Mice and rats
Alzheimer’s disease
model
Intravenous
(xenogenic
MSCs—human
MSCs)
Human MSCs were used.
Tisular PCR analyses (blood,
bone marrow, brain, spinal cord,
spleen, kidney, liver, heart, lung,
gonad) were used to assess
biodistribution.
Harvesting of tissues was performed at
24 h, 7 days, and 30 days after injection.
MSCs were broadly detected both in the
brain and several peripheral organs,
including the liver, kidney, and bone
marrow, of both species, starting within
7 days and continuing up to 30 days
post-transplantation.
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Tang et al.
[129] (2016)
Rats
Cirrhosis rats
(splenectomized)
Intravenous
(allogenic MSCs)
Qtracker705
nanoparticle-labelled MSCs
were infused.
Fluorescence imaging was
performed to assess
biodistribution.
Images were taken at 2 h and 5 days after
cell infusion.
Splenectomy improved the homing of
MSCs in the liver when compared to
non-splenectomy group.
Cao et al.
[130] (2016)
Rats
Healthy animals
Intravenous
(allogenic MSCs)
Luciferase and green fluorescent
protein were used to label MSCs.
Bioluminescence imaging, ex
vivo organ imaging,
immunohisto-chemistry (IHC),
and RT-PCR were used to assess
biodistribution.
Images were taken up to 1 month. After
that, histological analysis was performed.
MSCs were detected initially in the lungs
with subsequent distribution to liver,
kidneys and other abdominal organs. The
dorsal skin was also detected to have MSCs.
The signals disappeared at day 14.
Zhou et al.
[131] (2015)
Rats
Hepatic fibrosis
Selective intravenous
(superior mesenteric
vein)
(allogenic MSCs)
MSCs were double-labeled with
superparamagnetic iron oxide
and green fluorescent protein.
MRI, histology and qPCR tests
were used to assess
biodistribution.
MR imaging of the liver was carried out
before and 1, 3, 7 and 12 days after injection.
Liver, lung, kidney, muscle and heart
tissues were harvested at 1, 7, 15 and
42 days after cell injection.
Dual-labeled MSCs were retained in the
fibrotic liver of rats. SPIO particles and
EGFP-labeled BMSCs showed a different
tissue distribution pattern in rats with liver
fibrosis at 42 days after transplantation.
SPIO-based MR imaging
may not be suitable for
long-term tracking of
transplanted BMSCs in vivo.
Kim et al. [36]
(2015)
Mice
(athymic)
Brain tumor
Intravenous and
intracerebral
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with
near-infrared fluorescent dye.
Bioluminescence and
fluorescence imaging, qPCR and
histologic examinations were
performed.
Imaging techniques were performed at 1
and 4 h, 1, 7, 14 and 21 days.
MSCs resided predominantly in the lung
up to day 1 and the signal intensity
decreased over time. Many cells moved
from the lung toward other organs (liver
and spleen) after day 1, and the signal
remained stable in these regions for 14 days.
From day 1 to day 14, MSCs were clearly
detectable in the tumor area.
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Kim et al. [38]
(2015)
Beagle dogs
Spinal cord injury
Intravenous
(allogenic MSCs)
MSCs were labeled with green
fluorescent protein.
Ex vivo bioluminescence was
used to assess biodistribution.
Ex vivo examination was performed 7 days
after injection.
The green fluorescent protein-expressing
AD-MSCs were clearly detected in the lung,
spleen, and injured spinal cord; however,
these cells were not detected in the liver
and un-injured spinal cord.
Li et al. [45]
(2015)
Mice
Acute liver injury
Selective
intravenous: Inferior
vena cava (IVC),
superior mesenteric
vein (SMV) and
intrahepatic (IH)
injection.
(allogenic MSCs)
MSCs were labeled with
luciferase. Bioluminiscece
images were used to assess
biodistribution.
Images were taken at 3 h, and at 1, 3, 7, 10,
14 and 21 days.
After IVC infusion, MSCs were quickly
trapped inside the lungs, and no detectable
homing to the liver was observed. By IH
injection, lung entrapment was bypassed,
but MSCs-R distribution was only localized
in the injection region of the liver. After
SMV infusion, MSCs-R were dispersedly
distributed and stayed as long as 7-day
post-transplantation in the liver.
SMV is the optimal MSCs
delivery route for liver
disease.
Zhang et al.
[33] (2015)
Rabbit
Acute ischemic
kidney injury
Intravenous
(allogenic MSCs)
MSCs were labeled with SPION
particles. MRI images and
histological analysis were used
to assess biodistribution
Images and histological analysis were
taken at 1, 3, 5 and 8 days.
MSCs were detected up to 8 days, with a
maximum amount of cells at day 3.
No systemic distribution was assessed.
Schmuck et al.
[43] (2016)
Sprague-
Dawley
rats
Acute lung injury
(12 animals)
Intravenous
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with
QTracker65. 3D cryo-imaging of
lungs, liver, spleen, heart,
kidney, testis, and intestine was
performed to assess
biodistribution.
Tissue samples were collected and
analyzed at 60, 120 and 240 min and 2, 4
and 8 days after infusion.
Distribution up to 240 min was detected
mostly in liver, and also in lungs and
spleen.
The number of cells detected at 2, 4, and
8 days was less than 0.06% of the total cells
infused on day 0 and were mainly
distributed also in lungs, liver and spleen
but relatively higher captation was seen in
the rest of the tissues studied.
Authors conclude that
studies using
bioluminescence to track
cells underestimate cell
retention in the liver because
of its high tissue absorption
coefficient
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Li et al. [27]
(2018)
Rats
Silicosis
(54 animals)
Intravenous
(allogenic MSCs)
MSCs were labelled with
1,1′-dioctadecyltetramethyl
indotricarbocyanine iodide.
Fluorescence imaging was
performed to assess
biodistribution.
Images were taken 1 h, 6 h, 24 h, 3 days,
15 days, and 30 days after injection both
in vivo and ex vivo.
MSCs distributed mostly in liver and lungs,
with a peak at 6 h, and a dramatic decrease
by day 3. At day 30, no MSCs were
detected.
Distribution in lungs was
significantly higher in rats
with damaged lungs
compared to healthy rats.
Park et al.
[34] (2018)
Mice
Alzeimer’s disease
(53 animals)
Intravenous
(allogenic MSCs)
MSCs were 111In-tropolone
labeled. Imaging with SPECT
(in vivo) and gamma-counter
(ex vivo) was performed to
assess biodistribution.
Imaging and gamma-counter studies were
performed at 24 h and 48 h post infusion.
In Alzheimer’s model, brain uptake of
MSCs was significantly higher than in
healthy animals. In both groups, MSCs
distributed mainly to lungs, liver and
spleen.
Distribution to brain seem to
be higher in Alzheimer’s
models.
Leibacher
et al. [28]
(2017)
Mice
Healthy animals
(number unknown)
Intravenous
(xenogenic
MSCs—Human
MSCs)
Human MSCs were injected and
PCR techniques were used to
assess biodistribution by
searching for SRY sequences.
Ex vivo assessment was performed at
5 min, 30 min, 2 h, 6 h, and 24 h.
The majority of injected MSCs were
detected by qPCR in the lungs 5 min after
transplantation, whereas <0.1% were
detected in other tissues over 24 h
After intravenous injection,
most cells distribute to
lungs.
Yun et al. [31]
(2016)
Rats
Acute liver injury
Intravenous
(xenogenic
MSCs—Human
MSCs)
Human MSCs were injected and
PCR techniques were used to
assess biodistribution.
Mice were euthanized at 1, 3, 12, or 24 h
and at 1, 4, or 13 weeks post injection.
MSCs were detected soon in the lungs and
disappeared before 1 week post injection.
Then, MSCs were found mainly in the liver.
No MSCs were found in other tissues
(testis, ovary, spleen, pancreas, kidney,
adrenal gland, thymus, and brain).
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Abramowski
et al. [42]
(2016)
Mice
Experimental
autoimmune
encephalomyelitis
model
(number unknown)
Intravenous
(allogenic MSCs)
MSCs were injected and a
variety of techniques, including
magnetic resonance imaging,
immunohistochemistry,
fluorescence in-situ
hybridization, and quantitative
polymerase chain were
performed to assess
biodistribution.
Assessment was focalized in the brain area.
No evidence for immediate migration of
infused MSC into the central nervous
system of treated mice was found.
Kim et al. [30]
(2016)
Rats
Healthy rats
Intravenous
(allogenic MSCs)
MSCs were surface-modified
with HA—wheat germ
agglutinin (WGA) conjugate for
targeted systemic delivery of
MSCs to the liver and labeled
with fluorescent dyes.
Histologic examinations were
performed.
Assessment was performed at 4 h post
injection. Lungs and livers were collected.
HA-WGA-MSCs had a greater distribution
to the liver when compared to control
MSCs, which were mainly trapped in the
lungs.
HA-WGA conjugate has
great potential to deliver
MSCs to the liver efficiently
within a short time and to
reduce the entrapment of
MSCs in the lung.
Lu et al. [40]
(2016)
Mice
Acute distress
respiratory
syndrome model
Intravenous
(allogenic MSCs)
Fluorescein isothiocyanate–
dextran was used to label MSCs.
Histological analyses and qPCR
were used to assess
biodistribution.
Assessment was performed immediately
after cell injection, 2, 24, and 48 h later.
Lung, heart, spleen, kidney, brain, and liver
were collected.
MSCs accumulated mainly in the lungs of
control and diseased mice, with minor
amounts distributed to other organs up to
2 h. Diseased animals showed less early
distribution to lungs and higher
distribution to the rest of the organs when
compared to healthy animals.
Acute distress respiratory
syndrome might lessen the
pulmonary capillary
occlusion by MSCs
immediately following cell
delivery while facilitating
pulmonary retention of the
cells.
J. Clin. Med. 2021, 10, 2925
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Fabian et al.
[46] (2017)
Young and
old mice
Alzheimer disease
(unknown number)
Intravenous
(syngenic MSCs)
Histologic and genetic tests
(PCR) were performed to
evaluate MSCs distribution.
Genetic tests and histology were assessed
after 28 days.
Transplantation of MSCs obtained from old
mice showed biodistribution only in the
blood and spleen in both young and old
mice.
MSCs obtained from young mice showed a
wide distribution in young receptors (lung,
axillary lymph nodes, blood, kidney, bone
marrow, spleen, liver, heart, and brain
cortex). In contrast, these cells showed
distribution only in the brain cortex in old
mice.
Authors conclude that aging
of both the recipient and the
donor MSCs used attenuates
transplantation efficiency.
Ohta et al.
[37] (2017)
Rats
Spinal cord injury
Intravenous
(allogenic MSCs)
MSCs were labeled with
3H-thymidine. Histologic and
radioactivity examination of the
spinal cord segment containing
the damaged region, blood and
target organs were harvested.
After 3, 24 and 48 h, organs were collected
and radioactivity measured.
The highest radioactivity was detected in
the lungs 3 h after infusion, while
radioactivity in the injured spinal cord was
much lower. However, brain radioactivity
was lower than damaged spinal cord.
MSCs distribute to the
injured spinal crod.
Liu et al. [29]
(2018)
Mice
Acute lung injury
Intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with
fluorophore Cy7.
Histology was performed to
assess biodistribution.
Ex vivo assessment of lungs, heart, spleen,
kidneys and liver was performed at 30 min,
1 day, 3 days and 7 days following injection.
MSCs distributed to the lungs up to day 1;
and to the liver up to day 3, with
progressive subsequent decrease. No
significant distribution was observed to
heart, spleen and kidneys
J. Clin. Med. 2021, 10, 2925
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Qin et al. [41]
(2018)
Rabbits
Liver tumors
Intravenous
(allogenic MSCs)
MSCs were colabeled with
superparamagnetic iron oxide
(SPIO) particles and
4′,6-diamidino-2-phenylindole
(DAPI).
MRI and histologic examination
were performed.
MRI was performed at days 0, 3, 7 and 14
after cells transplantation. Histological
analyses were performed immediately after
the MRI examination.
MSCs were detected in the liver tumors,
rather than the non-tumor liver tissue and
other organs. At day 3, MSCs were mainly
in the central part of the tumor, showing a
posterior distribution in the periphery.
MSCs distribute mainly to
the damaged liver when
injected intravenously.
Leibacher
and
Henschler
[132] (2016)
Wistar rats
[133]
Transient cerebral
ischemia
(25 animals)
Intravenous and
intraarterial
(allogenic MSCs)
Feridex (Berlex Imaging) mixed
with the transfection agent
poly-l-lysine.
Later evaluation with MRI and
necropsies.
Imaging was performed before and after
the infusion (2 to 24 h after).
After intraarterial infusion, MSCs were
detected in the brain of the rats.
After intravenous infusion, no MSCs were
detected in the brain.
Authors conclude that MSCs
may engraft in peripheral
tissues after intraarterial
infusion. Intravenous
infusion might not be quite
effective to deliver MSCs to
peripheral tissues.
Mice [47]
Healthy animals and
acute kidney injury
(AKI) model
(Unknown number)
Intravenous and
intraarterial.
(allogenic MSCs)
Transfection with
luciferase-neomycin
phosphotransferase construct.
Later evaluation with Xenogen
IVIS 100 imaging system.
Imaging was performed immediately after
infusion, at 24 h, 72 h and 7 days.
Intravenous infusion led to a majority of
cells distributing to lungs.
Intraarterial infusion lacked pulmonary
retention and caused distribution to
kidneys, especially in AKI mice. MSCs
gradually disappeared after 24 h.
Intraarterial infusion might
be adequate when treating
kidney conditions.
Schubert et al.
[44] (2018)
Mice
Acute kidney injury
model
(Unknown number)
Intravenous.
(autogenic MSCs)
MSCs from luciferase transgenic
mice.
Evaluation was performed with
bioluminescence imaging and
RT-PCR.
Imaging was performed on days 1, 3 and 6.
RT-PCR was performed in kidney, lung,
liver tissue and blood on day 6.
Bioluminescence showed a high
distribution of MSCs to lungs on day 1,
which disappeared on days 3 and 6.
RT-PCR on day 6 showed variables
amounts of MSCs-mRNA in blood, liver
and kidneys
RT-PCR seems to be a more
sensitive technique to
demonstrate the late
presence of MSCs in
different tissues when
compared to
bioluminescence.
J. Clin. Med. 2021, 10, 2925
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Nakada and
Kuroki [62]
Mice
Healthy animals
(Unknown number)
Intravenous and
intramuscular
(allogenic MSCs)
MSCs were labelled with
chromium.
Laser ablation inductively
coupled plasma imaging mass
spectrometry (LAICP-IMS) was
used to assess biodistribution,
Detection time is not recorded.
After intramuscular injection, MSCs remain
in the muscular tissue.
After intravenous injection, MSCs are
detected in the lungs.
Authors conclude that
chromium labelling could be
a promising technique.
Mäkelä et al.
[22] (2015)
Pigs
Healthy animals (12
animals)
Intravenous and
intraarterial
(autogenic and
allogenic MSCs)
99mTc- hydroxymethyl-
propylene-amine-oxime.
Evaluation was performed with
SPECT/TC. Biopsies were also
performed.
Imaging was performed 8 h later.
Intravenous infusion led to a high
distribution of MSCs into the lungs.
Intraarterial infusion decreased the
deposition in the lungs and increased the
uptake in other organs, specially the liver
and kidneys.
Intraarterial infusion might
improve the distribution to
peripheral tissues and may
avoid pulmonary retention.
Wang et al.
[134] (2015)
Mice
Bone marrow
transplanted animals
Intravenous and
intraarterial
(xenogenic
MSCs—Human
MSCs)
99mTc- hydroxymethyl-
propylene-amine-oxime and
luciferase.
Bioluminescence, scintigraphy
and histologic examination were
used to assess biodistribution.
Bioluminescence was performed at 30 min,
24 h, 48 h, 96 h and once a week for up to
two month. Scintigraphic imaging and
X-ray imaging were performed at 5 h, 10 h
and 1 d after injection. After 2 months,
animals were sacrificed and ex vivo
histology was performed.
After intraarterial injection persistent
whole–body MSC distribution in
allo-trasplant recipients was shown, while
MSCs were rapidly cleared in the syngeneic
animals within one week. In contrast,
intravenous injected MSCs were mainly
seen in the lungs with fewer cells traveling
to other organs.
J. Clin. Med. 2021, 10, 2925
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Silachev et al.
[49] (2016)
Rats
Traumatic brain
injury model
Intravenous and
intraarterial
(allogenic MSCs)
9mTc and iron microparticles
labelled MSCs. Evaluation was
performed with SPECT/TC,
MRI and histology.
Evaluation was performed at 1 h and 16 h
after trasplantateion.
After intravenous injection, MSCs
distributed to lung, kidney, and partially in
the liver and bladder, with progressive
decrease to 16 h. After intraarterial
injection, MSCs distributed significantly to
damaged hemisphere.
Intraarterial injection
improves the distribution to
the damaged cerebral area.
Cao et al. [50]
(2018)
Rats
Orthotopic glioma
model
Intravenous,
intraarterial and
intratumoral
(allogenic MSCs)
MSCs were transduced to
express ferritin heavy chain and
green fluorescent protein.
MRI and histology evaluations
were performed.
MRI was performed at days 0, 1, 3, 5, 7 and
9 after cell injection. Histological analysis
was performed at days 8, 12 and 18.
Intravenous injection did not lead to
accumulation of MSCs in the tumor.
However, intralesional and intraarterial
injections showed a rapid accumulation of
MSCs in the core of the tumor with a
gradual decrease of the cells in the zone.
Intravenous injections does
not lead to MSCs migration
to central nervous system
tumors, whereas
intraarterial and
intralesional injections do.
Taylor et al.
[55] (2020)
Mice
Renal injury model
Intravenous and
intracardiac
(allogenic MSCs)
MSCs were labelled with
luciferase and SPIO. MRI and
bioluminescence were used to
assess biodistribution.
Images were taken up to 2 days after
injection.
Following intravenous administration, no
MSCs were detected in the kidneys,
irrespective of whether the mice had been
subjected to renal injury. After intracardiac
injection, MSCs transiently populated the
kidneys, but no preferential homing or
persistence was observed in injured renal
tissue.
J. Clin. Med. 2021, 10, 2925
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Table 2. Cont.
Article
Model
Disease (Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Scarfe et al.
[48] (2018)
Mice
Healthy animals
(unknown number)
Intravenous and
intracardiac (left
ventricle)
(allogenic MSCs and
xenogenic
MSCs—human
MSCs)
MSCs were labelled with
luciferase (Luc) or a bicistronic
construct of Luc and ZsGreen
for bioluminescence imaging.
For MR tracking, cells were
labelled with diethylaminoethyl-
dextran-coated
SPIONs.
In vivo biodistribution of cells was
monitored by BLI immediately after cell
administration and at multiple time points
up to 30 day. Ex vivo MRI at baseline and
up to 2 days post administration.
Intravenous MSCs distributed mainly to
the lungs.
Intracardiac MSCs distributed to the brain,
heart, lungs, kidney, spleen and liver, with
also a majority of cells distributing to the
lungs.
Intracardiac injection led to
a wide distribution of MSCs
to peripheral organs.
Table 3. Biodistribution after IA administration of MSCs in animal models.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Khabbal et al.
[51] (2015)
Rats
Ischemic stroke
model
Intraarterial (external
carotid)
(allogenic MSCs and
xenogenic
MSCs—Human
MSCs)
MSCs were labeled with 99mTc.
Whole body SPECT images and ex
vivo radioactivity measures were
used to assess biodistribution.
SPECT images were acquired 20 min, 3 h, and 6 h
postinjection, after which rats were sacrificed for ex
vivo examinations.
The majority of the cells were located in the brain
and especially in the ipsilateral hemisphere
immediately after cell infusion. This was followed
by fast disappearance. At the same time, the
radioactivity signal increased in the spleen, kidney,
and liver.
Human MSCs had faster
clearance from the brain
than rats MSCs.
Fukuda et al.
[56] (2015)
Rats
Ischemic stroke
model
Intraarterial
(Common carotid
artery)
(xenogenic
MSCs—human
MSCs)
Human MSCs were used and
labeled with PKH26.
Bioluminescence and anti-human
vimentin antibodies were used to
assess biodistribution of MSCs in ex
vivo histological analysis.
Examinations were performed 24 h post infusion.
MSCs were widely distributed throughout the
cortex and striatum of the ipsilateral hemisphere at
24 h after transplantation of MSCs.
J. Clin. Med. 2021, 10, 2925
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Table 3. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Cerri et al.
[52] (2015)
Wistar
rats
Parkinson’s
disease
(unknown
number)
Intraarterial. (One
group also received
mannitol to
transiently
permeabilize the
blood-brain barrier).
(allogenic MSCs)
MSCs were double-labelled:
CellVue NIR815 Kit for Membrane
Labeling (Polyscience, Warrington,
PA, http://www.polysciences.com)
(accessed on 25 June 2021)
and lipophilic red fluorescence dye
PKH26. Later histological
examinations assessed the
distribution of MSCs within the
brain.
Necropsies were performed 7 and 28 days after
infusion of MSCs.
Rats not treated with mannitol showed a very low
number of MSCs in the brain at 7 and 28 days
post-infusion. Rats treated with mannitol showed
a significantly higher number of MSCs within the
brain. At day 7, most of MSCs were in the blood
vessels, whereas at day 28, most of MSCs were in
the parenchyma.
Most of MSCs distributed in the same lateral
hemisphere where the infusion took place.
A strong MSCs signal in the lungs and spleen up to
28 days after infusion was detected.
Authors conclude that the
use of a permeabilizing
agent is essential to allow
passage of MSCs across the
blood-brain barrier.
A significant number of
infused cells accumulated in
the peripheral organs (liver,
lungs).
Jin et al. [135]
(2016)
Beagle
dogs
Osteonecrosis of
the femoral head
Intraarterial
(autogenic MSCs)
MSCs were labeled with
5-bromo-2-deoxyuridin. Histologic
examinations (right femoral head,
heart, lung, liver, spleen, kidney,
gallbladder, small bowel, pancreas,
prostate, and testicle) were
performed to assess biodistribution.
Histologic examinations were performed 8 weeks
after cell infusion.
Organs had uneven distribution of MSCs: Heart,
liver, gallbladder, kidney and stomach had the
major quantity of MSCs.
Arnberg et al.
[58] (2016)
Rabbit
Healthy rabbits
Intraarterial infusion
(superior mesenteric
artery) and
intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with
11In-oxinate.
SPECT-TC images were used to
assess biodistribution.
SPECT-TC was performed at 6 h and at 1, 2, and
5 days post infusion.
Intravenous administration resulted in early and
long distribution of MSCs to the lungs. In contrast,
selective intraarterial injections resulted in MSCs
distribution in the intestine and in the liver.
Selective intraarterial
delivery could improve the
results in treating some
localized diseases.
Espinosa et al.
[59] (2016)
Horses
Healthy horses
Intraarterial selective
infusion (median
artery)
(allogenic MSCs)
MSCs were labeled with
99mTc-HMPAO. Scintigraphic
images were taken to assess
biodistribution.
Images were taken at the time of injection and at 1,
6, and 24 h postinjection.
Homogeneous distribution of radiolabeled MSC
was observed through the entire distal limb,
including within the hoof. Systemic
biodistribution was not assessed.
J. Clin. Med. 2021, 10, 2925
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Table 3. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Sierra-
Parraga et al.
[57] (2019)
Pigs
Renal ischemia-
reperfusion
injury.
(unknown
number).
Intraarterial infusion
(renal artery)
(allogenic MSCs)
MSCs were labelled with
fluorescent compunds. Flow
cytometry and genetic tests (PCR)
were done in blood and tissues.
Samples were collected 30 min and 8 h after
infusion.
After infusion, a minor number of MSCs left the
kidney through the renal vein, and no MSCs were
identified in arterial blood. A low percentage of
the infused MSCs were present in the kidney
14 days after administration.
Most of MSCs were trapped in the renal cortex.
Renal intra-arterial MSC
infusion seem to limit
off-target engraftment,
leading to efficient MSC
delivery to the kidney.
Barthélémy
et al. [60]
(2020)
Golden
Re-
triever
Dogs
Duchenne
muscular
dystrophy model
Intraarterial (femoral
artery)
(not stated)
MSCs were labeled with 111In-oxine.
Scintigraphy was performed to
assess biodistribution.
Scintigraphic images were taken immediately after
injection and at 1, 2, 24, 48 h and 1 week.
Immediately after injection, MSCs were trapped in
the capillary network of the limb and in the lungs.
Subsequently, MSCs were also mainly in the
injected limb, with a decrease in the lung captation
and a relative increase in the liver captation.
Table 4. Biodistribution after intramuscular and intraarticular administration of MSCs in animal models.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Hamidian
Jahromi et al.
[63] (2017)
Mice
Carrageenan-
induced plantar
inflammation
Intramuscular
(contralateral to
plantar
inflammation)
(xenogenic
MSCs—Human
MSCs)
MSCs were labelled with Gaussia
Luciferase.
Bioluminescence imaging, qPCR
and histology techniques were used
to assess biodistribution.
Bioluminescence was performed at 24 h, 48 h and
up to 33 days.
No MSCs were found to distribute to other organs.
MSCs were detectable in the muscle up to 33 days
after injection.
MSCs were able to reduce
the contralateral
inflammation and to lower
the TNF-alfa serum levels
without distributing
systemically.
J. Clin. Med. 2021, 10, 2925
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Table 4. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Creane et al.
[61] (2017)
Mice
Healthy mice
(10 animals)
Intramuscular
(xenogenic
MSCs—Human
MSCs)
Human MSCs were injected and
quantitative PCR for Alu sequences
was performed in different tissue
samples.
Ex vivo analysis was performed 3 months after
injection.
No MSCs were detected in any organ, including
heart, lung, brain, liver, kidney and spleen. MSCs
were detected in the thigh and calf samples, where
MSCs were injected.
Intramuscular MSCs do not
seem to remain viable
and/or distribute 3 months
after injection.
Hamidian
Jahromi et al.
[65] (2019)
Rats
and
mice
(Re-
view)
Different diseases
Intramuscular
(different sources of
MSCs)
Different techniques.
MSCs do not seem to distribute after intramuscular
injection. MSCs seem to remain or spread locally,
without systemic biodistribution.
Intramuscular MSCs do not
seem to distribute
systemically.
Cai et al. [64]
(2017)
Rats
Healthy rats
Intramuscular
(allogenic MSCs)
Melanin-based gadolinium3+
(Gd3+)-chelate nanoparticles were
used to label MSCs.
MRI was used to assess
biodistribution.
MRI was performed on days 1, 4, 7, 14, 21, and 28.
MSCs were found in the muscle up to 28 days after
injection. No systemic biodistribution was
observed.
Intramuscular MSCs do not
seem to distribute
systemically
Markides
et al. [70]
(2019)
Sheep
Osteochondral
injury
Intraarticular
(autogenic MSCs)
MSCs were labelled with Nanomag,
and using a cell-penetrating
technique,
glycosaminoglycan-binding
enhanced transduction (GET).
Evaluation was performed with ex
vivo MRI and histologic tests.
Ex vivo MRI and histology was performed 7 days
after injection.
MSCs were detected in the synovium, and not in
the osteochondral defect.
MSCs are capable to home in
the synovium, whereas they
do not seem to be able to
enter the joint to reach the
osteochondral defect.
Yang et al.
[74] (2019)
Mice
Supraspinatus
tendon tear
Intraarticular
(allogenic MSCs)
MSCs were labeled with quantum
dots with near-infrared properties.
Near-infrared fluorescence imaging
was used to assess biodistribution.
Imaging was performed at days 1, 3, 7, 11, 14, and
17.
MSCs did not distribute systemically. MSCs
tended to migrate from the joint to the place of the
lesion.
J. Clin. Med. 2021, 10, 2925
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Table 4. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Satué et al.
[75] (2019)
Rats
Patellofemoral
cartilage defect
Intraarticular
(allogenic MSCs)
MSCs expressing heat stable human
placental alkaline phosphatase were
used. Histological and
immuno-histochemical analyses
were performed in joint tissue and
distant organs (heart, spleen,
kidney, liver and lung)
Ex vivo analysis was performed at 1 day, 1 week, 1,
2 and 6 months.
Injected MSCs remained in the synovial cavity,
engrafted within the cartilage lesion, and were
detectable up to 1 month post-injection. No
systemic distribution was observed, apart from 1
case of MSCs in the lung.
Li et al. [67]
(2016)
Mice
Osteoarthritis
Intraarticular
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with DiD
fluorescent dye. In vivo
bioluminescence imaging, and ex
vivo quantitative PCR were
performed to assess biodistribution.
Ex vivo imaging was performed up to day 70. PCR
was performed at day 14 and 70 in heart, liver,
spleen, lung, kidney, brain, muscle adjacent to the
joint, and the whole injected knee join.
MSCs were detected in the injected joint up to day
70 in diseased mice. In healthy mice, MSCs were
detected up to day 21.
No systemic distribution of MSCs was found.
MSCs seem to stand long
times in the injected joint
with no systemic
distribution.
Marquina
et al. [104]
(2017)
Rats
Intraarticular
chondrocyte
trasplantation
Intraarticular,
intravenous,
intraperitoneal
(allogenic MSCs)
MSCs were labeled with luciferase.
Bioluminescence imaging was
performed to assess biodistribution.
Imaging was performed at 2 h, 24 h, 2, 4 and 5 days.
After intraarticular injection, no distribution of
MSCs was detected.
After intravenous injection, most MSCs were
trapped in the lungs and disappeared within 24 h.
After intraperitoneal injection, MSCs were
localized in the injection site without distribution
up to 5 days.
Li et al. [68]
(2017)
Rats
Osteoarthritis
Intraarticular
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with DiD
fluorescent dye. In vivo
bioluminescence imaging and ex
vivo histologic examinations were
performed.
In vivo imaging was performed up to 70 weeks.
MSCs were detected in the injected join up to
9 weeks. No systemic distribution was observed.
MSCs seem to stand long
times in the injected joint
with no systemic
distribution.
J. Clin. Med. 2021, 10, 2925
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Table 4. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Meseguer-
Olmo et al.
[21] (2017)
Rabbits
Healthy animals
Intraarticular and
intravenous
(xenogenic
MSCs—human
MSCs)
MSCs were labeled
with99mTc-HMPAO. Scintigraphic
images and qPCR in tissues (liver,
kidney, heart, lung, bladder, knee,
gallbladder) were used for assessing
biodistribution.
Images were taken every 30 s during 25 min. qPCR
was performed at 24 h.
Intravenous MSCs distributed mainly to the lungs.
Intraarticular MSCs did not distributed.
Toupet et al.
[66] (2015)
Mice
Osteoarthritis
and arthritis
(unknown
number)
Intravenous and
intraarticular
(xenogenic
MSCs—human
MSCs)
Human MSCs were infused,
Quantitative assays for human
DNA and mRNA were used to
evaluate the distribution in 13
different organs.
Necropsies were performed at different times (1,
10, 30, 42) and PCR was performed.
After intravenous infusion, MSCs were only
detected in lungs in day 1. No MSCs were detected
in day 10.
After intra-articular injection, MSCs were detected
for at least 10 days in osteo-arthritic knee joints.
No MSCs were detected in other organs after in
these mice.
After intra-articular
injection, MSCs do not seem
to distribute to other organs
or tissues.
Shim et al.
[73] (2015)
Mice
Osteoarthritis
and healthy
models
Intraarticular and
intravenous
(xenogenic
MSCs—human
MSCs)
Human MSCs were injected and
qPCR tests were used to assess
biodistribution in the different
organs.
At 15 min and 8 h after injection, samples were
collected from eight organs (spleen, kidney, liver,
lymph nodes, muscle, lung, heart, brain). Blood
concentrations were also monitored.
After intravenous injection MSCs were detected
immediately in blood, with a progressive decrease.
After intraarticular injection, MSCs were detected
in blood with a peak at 8 h.
No systemic distribution was observed after
intraarterial delivery. After intravenous injection,
most MSCs were trapped in the lungs.
After intraarterial injection,
MSCs are detectable in
blood with a peak at 8 h.
However, no systemic
distribution is observed.
Delling et al.
[69] (2015)
Sheep
Osteoarthritis
Intraarticular
(autogenic MSCs)
MSCs were labelled with SPION
particles.
MRI and histological analyses were
performed.
MR images were acquired at injection and at 1, 4, 8,
and 12 weeks. Ex vivo histological examination
was performed at 12 weeks.
MSCs were found in the joint up to 12 weeks,
without systemic distribution.
J. Clin. Med. 2021, 10, 2925
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Table 4. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Ikuta et al.
[76] (2015)
Rats
Healthy and
cartilage defect
models
Intraarticular (a
magnet was used for
selective
accumulation of
MSCs) and
intravenous
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with DiR
fluorescent dye and iron
nanoparticles.
MRI and fluorescent imaging were
used to assess biodistribution.
Histological exams were also
performed.
Bioluminescence imaging was performed
immediately and 1, 3, 7, 14, 21, and 28 days after
cell transplantation. At day 28, organs were
collected for ex vivo analyses. After intraarticular
injection, MSCs remained in the joint. The use of
the magnet led to magnetic MSCs accumulation in
the target lesion.
The use of a magnet during
magnetic-labeled MSCs
transplantation can lead to
selective accumulation of
cells into the cartilage
defects.
Table 5. Biodistribution after intralesional administration (except for intra-central nervous system) of MSCs in animal models.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Dave et al.
[54] (2017)
Mice
Chronic bowel
inflammation
Intra-cardiac
(xenogenic
MSCs—human
MSCs)
MSCs were labeled with luciferase
and red fluorescent protein.
In vivo and ex vivo
bioluminescence and histologic
examinations were performed to
assess biodistribution.
Images were taken up to 24 h after injection.
Histology was performed at 24 h post injection.
MSCs in healthy mice distributed mainly to
lungs, spleen and liver. In contrast, MSCs in
diseased mice were located mainly in the
intestine, with low pulmonary captation.
After intracardiac injection,
MSCs are able to distribute
mainly to the inflamed
intestine.
Jiang et al.
[109] (2018)
Rats
Myocardial
infarction model
(repeated
ischemia model)
Intra-myocardial
(allogenic MSCs)
MSCs were harvested from male
rats and injected into female rats.
qPCR was performed in different
tissues to assess biodistribution
(heart, lungs, spleen and liver)
Examinations were performed 3 weeks after
injection.
MSCs had a greater homing in heart and a
lower distribution to peripheral organs when
repeated ischemia was applied.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Bansal et al.
[108] (2015)
Mice
Healthy model
Intra-myocardial and
intravenous
(allogenic MSCs and
xenogenic
MSCs—Human
MSCs)
MSCs were labeled with
89Zr-desferrioxamine. PET scans
and radioactivity analyses were
performed to assess biodistribution
PET was performed at days 2, 4, and 7. Ex vivo
radioactivity analyses were performed at day 7.
After intra-myocardial injection, MSCs were
retained in the myocardium, as well as
redistributed to the lung, liver, and bone.
Intravenously administered MSCs also
distributed primarily to the lung, liver, and
bone.
Blazquez et al.
[107] (2015)
Pigs
Myocardial
infarction model
Intrapericardial
(allogenic MSCs)
MSCs were labelled with SPION
particles.
Biodistribution was assessed with
MRI, histology and PCR.
MRI was performed at days 3, 5 and 7.
MSCs were detected to home mainly in the left
ventricle. They were also detected in the right
ventricle, and both atriums.
After intrapericardial
injection, MSCs distribute
mainly to left ventricle.
Lebouvier
et al. [78]
(2015)
Pigs and
mice
Osteonecrosis of
the femoral head
Intraosseous
(xenogenic
MSCs—Human
MSCs)
Human MSCs were injected and
qPCR, cytometry and histologic
analysis was performed to assess
biodistribution in different tissues
(Femoral head, adyacent tissues,
liver, kidneys, spleen, and lungs).
Tissues were collected at either 30 min or 24 h
after injection.
No MSCs were detected in other organs apart
from the injection site.
Khan et al.
[71] (2018)
Mice
Tendon injury
Intralesional
(autogenic MSCs)
MSCs were labelled with
fluorescent-conjugated magnetic
iron-oxide nanoparticles (MIONs)
and were tracked with MRI,
histology and flow cytometry.
Tendons were recovered post mortem at 1 day,
and 1–2, 4, 12 and 24 weeks after MSC injection.
MSCs distributed throughout the tendon
synovial sheath but restricted to the synovial
tissues, with no MSCs detected in the tendon
or surgical lesion. After day 14, no MSCs were
detected.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Burk et al.
[72] (2016)
Horse
Tendon injury
Intralesional
(autogenic MSCs)
MSCs were 10106 Molday ION
Rhodamine B-labeled.
Biodistribution was assesd with
MRI, flow cytometry and histology
Tracking techniques were performed up to
24 weeks after injection. Labeled cells could be
traced at their injection site by MRI as well as
histology for the whole follow-up period of
24 weeks. Furthermore, small numbers of
labeled cells were identified in peripheral
blood within the first 24 h after cell injection
and could also be found until week 24 within
the contralateral control tendon lesions that
had been injected with serum
Ryska et al.
[106] (2017)
Rats
Fistula model in
Crohn’s disease.
Intralesional
(perifistula)
(allogenic)
MSCs were labeled with luciferase.
Bioluminescence imaging was
performed to assess biodistribution.
Imaging was performed at days 0, 2, 7, 14 and
30. MSCs distributed only in the injection site,
with a high reduction of luminescence by day 2.
MSCs were detectable up to day 30.
No systemic distribution
was shown after
intralesional injection.
Zhu et al. [82]
(2015)
Rats
Ovarian injury
Intraovaric and
intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were fluorescent labeled with
PKH26. Ex vivo bioluminescence
techniques were used to assess
biodistribution (brain, liver, kidney,
urocyst, ovary and uterus were
collected).
Bioluminescence was performed 1, 15, 30 and
45 days after injection.
After intraovaric injection, MSCs were detected
only in ovaries and uterus. After intravenous
injection MSCs were detected in liver, kidney,
ovary and uterus.
Sadeghi et al.
[79] (2016)
Rats
Birth-trauma
injury (urinary
disfunction)
(285 animals)
Intraurethral and
intravenous
(xenogenic
MSCs—Human
MSCs)
Alu genomic repeat staining,
PKH26 labeling, and
luciferase-expression labeling.
Histologic, genetic and
bioluminescence tests were
performed to evaluate MSCs
distribution.
Different assessments were performed at 0, 1, 4
and 10 days after injection.
No positive Alu-stained nuclei were observed
in urethras at 4, 10, and 14 days.
PKH26-labelled cells were found in all urethras
at 2 and 24 h. Bioluminescence study showed
increased luciferase expression from day 0 to 1
following injection, with a progressive
disappearance until day 7.
No MSCs were detected in
periurethral tissue after
intravenous injection.
MSCs were detected for less
than 7 days in periurethral
tissues after local injection.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Li et al. [136]
(2017)
Rabbits
Chronic
salpingitis model
Intrauterus and
intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with green
fluorescent protein and cyto-keratin
7. Ex vivo bioluminescence imaging
was performed in different organs
(oviduct, uterus, liver, and bladder).
The assessment was performed 1 week after
perfusion.
No clear results are derived from this study.
MSCs were detected in the uterus, bladder and
oviduct.
Ryu et al. [80]
(2018)
Sprague-
Dawley
rats
Interstitial
cystitis/bladder
pain sindrome
(unknown
number)
Injection into the
outer layer of the
bladder.
(xenogenic
MSCs—Human
MSCs)
Genetic transduction with green
fluorescent protein was wed for
labelling.
Longitudinal microcystoscopy
(combining confocal microscopy
and cystoscopy) was used to assess
the distribution of MSCs.
Images were obtained between 3 and 42 days
after transplantation.
The number of cells detected decreased rapidly
until day 7 and later decreased gradually until
day 42.
After day 30, MSCs migrated from the serosa
and muscularis layers to the urothelium. At
day 30, most of the cells were distributed in
vascular structures.
MSCs are capable of
migrating through the layers
of the bladder and might be
able to differentiate into
perivascular cells after day
30 post injection.
Dou et al.
[81] (2019)
Rats
Erectile
dysfuncion
(unknown
number)
Intra-cavernosal.
(xenogenic
MSCs—Human
MSCs)
MSCs were labelled with mKATE
and Renilla reniformis luciferase.
Bioluminescence was used to assess
the biodistribution. Histologic
samples were obtained from penis,
kidney, liver, lung, heart, skin,
prostate, testis and spleen.
Bioluminescence was performed immediately
after injection and up to 60 min. Histologic
samples were obtained at days 1, 3 and 7 after
injection.
In vivo, MSCs immediately distributed in the
para-penile region. An early migration to the
abdominal area was noted, where the cells
remained up to day 1.
Histologic examinations showed MSCs in the
penile, kidney, prostate and hepatic tissues.
Bioluminescence might be
less sensitive to detect MSCs
in distant tissues.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Kallmeyer
et al. [114]
(2020)
Rats
Cutaneous
wound
Intradermal and
intravenous
(allogenic MSCs)
MSCs were labeled with luciferase
and green fluorescent protein.
Bioluminescence imaging and
immunohistological analysis were
performed to assess biodistribution.
Imaging was performed at 3 h, 24 h, 48 h, 72 h
and 7 and 15 days.
Intravenous MSCs were detected in the lungs
3 h after injection with a signal disappearance
from 72 h. No MSCs were detected in the
wound. Locally administered MSCs remained
strongly detectable for 7 days at the injection
site without systemic distribution.
Tappenbeck
et al. [112]
(2019)
Mice
Healty animals
(unknown
number)
Intradermal and
intravenous
(xenogenic
MSCs—Human
MSCs)
Human MSCs were injected and
genetic tests (quantitative PCR)
were done in tissue samples: blood,
skin/subcutis and skeletal muscle
at the injection site, lymph node,
liver, spleen, lungs, brain, femur
bone, and bone marrow, kidneys,
thymus, thyroid/para-thyroid
gland and ovaries or testes) to
evaluate biodistribution.
After intradermal injection, mice were
sacrificed at 1 week, 3 months and 4 months.
After intravenous injection, mice were
sacrificed.
After intradermal injection, MSCs were
detected in the skin up to 3 months and also in
draining limph nodes after 1 week. No MSCs
were detected in any other tissues.
After intravenous injection, MSCs were
detected mainly in the skin and muscle near to
the injection site and also in the lungs on day 8.
After 1 month, most MSCs were in the lungs.
MSCs were also detected in low quantities in
kidney and thymus after 1 month.
After intradermal injection,
MSCs seem to remain in the
skin and migrate to lymph
node, without significant
systemic distribution.
Zhou et al.
[137] (2017)
Mice
Immune deficient
mice
Intradermal (a slice
of cells).
(xenogenic
MSCs—canine
MSCs)
MSCs were labeled with ultrasmall
super-paramagnetic Fe3O4
nanoparticles (USPIO). MRI was
used to assess biodistribution.
MRI was performed at 1 week, 4 weeks and
12 weeks after transplanting the cell sheets.
MSCs were detected up to 12 weeks with
gradual decrease of the captation.
Pratheesh
et al. [113]
(2017)
Rabbits
Cutaneous
wound
Intradermal
(xenogenic
MSCs—goat MSCs)
MSCs were labeled with PKH26.
Fluorescent microscopy was
performed to assess biodistribution
within the wound.
Skin samples were collected from respective
wounds on 3, 7, 10 and 14 days.
MSCs demonstrated a diffuse pattern of
distribution initially and were later
concentrated towards the wound edges and
finally appeared to be engrafted with the newly
developed skin tissue.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Léotot et al.
[77] (2015)
Mice
Immunodeficient
mice
MSCs were
pre-loaded into the
bone graft
(xenogenic
MSCs—Human
MSCs)
Human MSCs were used and qPCR
tests were used to assess
biodistribution.
Constructs and organs (liver, spleen, lungs,
heart, and kidneys) were harvested 24 h or
each week between 1 and 7 weeks after
implantation procedures.
No biodistribution of MSCs was detected.
MSCs were detectable in the graft up to 6
weeks.
Lopez-
Santalla et al.
[103] (2017)
Mice
Colitis
Intranodal injection
(inguinal nodes)
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with luciferase.
Biodistribution was assessed with
bioluminescence imaging.
Bioluminescence imaging was performed 48 h
after injection.
MSCs mainly remained in the injected lymph
nodes or fat surrounding them 48 h after
injection. No significant systemic distribution
was found, although the amount of MSCs in
the intestine was relatively high.
After intranodal injection,
most MSCs remained in the
injection site 48 h later.
Packthongsuk
et al. [105]
(2018)
Pigs
Healthy animals
Intraperitoneal
(autogenic MSCs)
MSCs (in this case, isolated from
Wharton’s Jelly) were labeled with
SRY sequences and PKH26-labeled
Ex vivo evaluation was performed
with qPCR and confocal microscopy.
Tissues were collected from the
heart, lung, pancreas, liver, kidney,
omentum, stomach, intestine,
uterine horn, ovary, muscle, and
bone marrow.
Biodistribution was assessed at 6 h, 24 h, and 7,
14 and 21 days after administration.
All tissues were positive for MSCs for 1-day-,
1-week-, 2-week-, and 3-week-old recipients.
MSCs-injected IP
consistently reached tissues
throughout the body. This
result indicates that
intaperitoneal injection
should be considered in
MSCs transplantations.
Hsu et al.
[102] (2017)
Mice
Severe combined
immunodefi-
ciency
Intrahepatic and
intrasplenic
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with luciferase,
red fluorescent protein and herpes
simplex virus-1 thymidine kinase.
PET, CT, bioluminescence imaging
and histological analyses were
performed to assess biodistribution.
Images and ex vivo analysis were collected for
weeks 1 to 4.
The intrahepatic group showed a confined
signal at the injection site, while the
intrasplenic group displayed a dispersed
distribution at the upper abdominal liver area,
and a more intense signal.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Liu et al.
[100] (2017)
Mice
Healthy and
NK-activated
mice
(unknown
number)
Intrahepatic
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with the
Luc2-mKate2 dual-fusion reporter
gene.
Bioluminescence was performed to
assess biodistribution.
Images were collected at multiple time points.
Bioluminescence imaging showed a gradual
decline in the signal in the liver in both groups.
NK-activated group showed a significantly
more rapid decrease in the signal.
NK cells seem to have a role
in the elimination of MSCs
transplanted into the liver.
Xie et al. [99]
(2019)
Rats
Acute liver injury
(unknown
number)
Intrahepatic
(xenogenic
MSCs—Human
MSCs)
MSCs were transduced sith
hHNF4α and luciferase2-mKate2
genes.
Bioluminescence imaging was used
to track their biodistribution.
Imaging was performed immediately after
transplantation and until disappearance of
cells.
MSCs were only distributed in the liver. They
were cleared within a short time after
transplantation.
Yaochite et al.
[101] (2015)
Mice
Stretozotocin-
induced diabetes
mellitus
(unknown
number)
Intrapancreatic and
intrasplenic
(allogenic MSCs)
MSCs were labelled with d-luciferin.
Bioluminescence imaging
techniques were used to assess the
biodistribution.
In vivo analysis was performed 0, 1, 3, 5, 8 and
11 days after injection. Ex vivo analysis were
performed 2 days after injection.
Intrasplenic MSCs were retained in the spleen
and distributed to the liver, with a progressive
decrease up to 8 days.
Intrapancreatic MSCs did not distribute to
other organs, and had a progressive decrease
up to 8 days.
Instrasplenic MSCs are
capable of distribute to the
liver.
Intrapancreatic MSCs do not
seem to be able to distribute
to other organs.
Lopez-
Santalla et al.
[103] (2018)
Mice
Colitis
Intraperitoneal
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with luciferase.
Bioluminescence was used to assess
the biodistribution.
Biodistribution of MSCs was measured in the
main organs (liver, spleen, intestine, lungs,
heart and blood) and lymph nodes (LNs,
inguinal, popliteal, parathymic, parathyroid,
mesenteric, caudal and axillary) 48 h after injection.
Most MSCs distributed to abdominal organs
(liver, spleen and intestine), with few
remaining in lymph nodes, lungs, blood and
heart. Biodistribution did not change
significantly between healthy and diseased mice.
Intraperitoneal injection
seems to lead to abdominal
spreading of MSCs.
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Table 5. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Chen et al.
[110] (2020)
Rats
Broncopulmonary
dysplasia
Intratracheal
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with Green
Fluorescent Protein and luciferase.
Bioluminescence was used to assess
the biodistribution in the lungs.
Images were taken every 5 s up to 1 min.
MSCs distributed in the lungs without
systemic distribution.
Intratracheal injection lacks
systemic distribution of
MSCs.
Cardenes
et al. [111]
(2019)
Sheep
Acute respiratory
syndrome
Intrabronchial and
intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were labeled with 18FDG.
PET-TC was performed to assess
biodistribution.
Images were taken 1 and 5 h after cell
administration.
After intrabronchial administration, MSCs
remained in the injection site at 1 and 5 h
without systemic distribution.
After intravenous injection, MSCs distributed
widely to organs, but with a preference for the
lungs.
Both administration routes
are convenient for treating
acute respiratory syndrome.
Table 6. Biodistribution after intra-central nervous system administration of MSCs in animal models.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Li et al. [98]
(2015)
Different animals and models
(the article is a review)
Intranasal
(different sources)
Different techniques.
Some results are:
•
MSCs reached an intracerebral glioma site within 6 h after i.n. delivery,
with a further significant increase in cell numbers within 24 h;
•
Intranasal application of MSCs resulted in the appearance of cells in the
olfactory bulb, brain and spinal cord, and about one-fourth of MSCs
survived for at least 4.5 months in the brain.
Zhang et al.
[138] (2017)
Rats
Spinal cord
injury
Intra-spinal cord
(allogenic MSCs)
MSCs were labeled with
Gd-DTPA-FA and
neurofilament-200. MRI and
histological examinations were
performed to assess biodistribution.
Examinations were performed at day 1, 7, 14
and 28 post delivery.
In the first 7 days, transplanted cells were
observed near the injection point. The number
of cells reached a maximum at day 14 and then
gradually distributed along the segmental
injury. No systemic distribution was observed.
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Table 6. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Barberini et al.
[83] (2018)
Horses
Healthy and
myelopathy-
model animals.
(9 animals)
Intrathecal, both
atlanto-occipital (AO)
and lumbo-sacral
(LS) injection.
(allogenic MSCs)
99mTc-HMPAO was used to label
MSCs.
Later evaluation was performed
with a gamma camera and
histologic samples.
Imaging was performed each hour until 5 h
post-infusion.
MSCs administered by AO
injection were found to distribute caudally
through-out the vertebral canal.
MSCs administered by LS injection did not
distribute cranially.
Histologic tests did not show the presence of
MSCs in diseased areas.
LS injection of MSCs does
not seem to be proper to
treat central nervous system
distant lesions.
Quesada et al.
[85] (2019)
Mice
Non-obese
diabetic severe
combined im-
munodeficiency
mice
Intrathecal
(xenogenic
MSCs—Human
MSCs)
Human MSCs were used.
Histologic evaluation and qPCR
were performed in different tissues
(Heart, brain, cerebellum, spinal
cord, liver, spleen, lungs, kidneys
and gonads).
Evaluation was performed 24 h and 4 months
after injection.
24 h post-injection, MSCs were detected in the
spinal cord and in 1 heart.
4 months after injection, MSCs were detected
in 3 hearts and in 1 brain.
Kim et al. [84]
(2020)
Rats
Healthy rats
Intrathecal (injected
via L2-L3 space)
(xenogenic
MSCs—Human
MSCs)
Fluorescent dye DiD was used to
label MSCs. Ex vivo
bioluminescence and qPCR of brain,
spine and heart, lung, liver, spleen,
and kidney was used to assess
biodistribution.
Imaging was performed at 0, 6, and 12 h post
injection. MSCs were detected in the spinal
cord at all times. MSCs were found in the brain
only at 12 h. No other organs showed MSCs.
Increasing the Cell Injection dose of MSCs
improved the migration of MSCs to the brain.
MSCs are able to migrate
from spinal cord to the brain.
This migration can be
improved by the increase of
the dose.
Violatto et al.
[97] (2015)
Mice
Amyotrophic
lateral sclerosis
model
Intracerebral (lateral
ventricles) and
intravenous
(xenogenic
MSCs—Human
MSCs)
MSCs were double labeled with
fluorescent nanoparticles and
Hoechst-33258. Bioluminescence
and histologic examinations were
used to assess biodistribution.
In vivo and ex vivo analyses were performed
at 1, 7, 21 days.
By intravenous administration cells were
sequestered by the lungs and rapidly cleared
by the liver. MSCs transplanted in lateral
ventricles remained on the choroid plexus for
the whole duration of the study even if
decreasing in number. Few cells were found in
the spinal cord, and no migration to brain
parenchyma was observed
J. Clin. Med. 2021, 10, 2925
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Table 6. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Geng et al.
[91] (2015)
Rats
Cerebral
ischemia
Intracerebral
(allogenic MSCs)
A gadolinium-based cell labeling
technique was used.
MRI images were used to assess
biodistribution.
MRI was used to image the cells 1,3, 5 and
7 days after the Gd-MSC injection.
MSCs did not distribute systemically.
Mastro-
Martinez et al.
[90] (2015)
Rats
Traumatic brain
injury
Intracerebral
(allogenic MSCs)
Green fluorescent protein was used
to label cells.
Histological examinations and
immunochemistry were used to
assess biodistribution.
Histologic examination was performed at 24 h
and 21 days after transplantation.
MSC were found in the perilesional area at
24 h, and their number decreased with time
after transplantation. MSC treatment increased
the cell density in the hippocampus and
enhanced neurogenesis in this area.
Park et al.
[96] (2016)
Beagle
dogs
Healthy animals
Intracerebral
(intra-ventricular)
(xenogenic
MSCs—Human
MSCs)
Human MSCs were used.
Immunohistochemical and qPCR
were performed to assess
biodistribution.
Brains were collected 7 days after infusion.
MSCs migrated from ventricles towards the
cortex, being found in the brain parenchyma,
especially along the lateral ventricular walls.
MSCs were also detected in the hippocampus
and the spinal cord.
No systemic distribution of MSCs was
detected.
Xie et al. [87]
(2016)
Rats
Intracerebral
hemorrhage
Intracerebral and
intravenous
(xenogenic
MSCs—Human
MSCs)
A fluorescent dye was used to label
MSCs (CM-DiI). Histologic
evaluation was used to assess
distribution of MSCs.
Histologic examination was performed at 28
days.
After intracerebral injection, MSCs stayed in
the injection place, distributed around the
hemorrhage. A small amount of cells migrated
to the contralateral hemisphere. After
intravenous injection, MSCs were also found in
the cerebral area.
Both intracerebral and
intravenous routes are
appropriate for treating
intracerebral hemorrhage.
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Table 6. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Duan et al.
[88] (2017)
Rats
Cerebral
ischemia
(54 animals)
Intracerebral
injection (right
striatum)
Green fluorescent protein MSCs
(GFP-MSCs) and SPION labeled.
MRI and histology were used to
assess biodistribution.
Imaging and/or histology were performed
weekly from week 1 to 8 weeks after cells
transplantation.
MSCs were found to remain in the area in a
high quantity in week 1. Later, MSCs number
decreased drastically, being detectable up to
week 8. A small amount of cells migrated to
corpus callosum.
Dong et al.
[95] (2017)
Rats
Brain traumatic
injury
(30 animals)
Intracerebral
injection
(intraventricular)
(allogenic MSCs)
Green fluorescent protein MSCs
(GFP-MSCs).
Imaging techniques and histology
were used to assess biodistribution
in blood vessels.
Techniques were performed at 10, 14, and
17 days. MSCs were found to home in large
arteries (thoracic aorta, abdominal aorta,
common iliac artery) 10, 14, and 17 days after
transplantation.
MSCs seem to distribute
after brain injury when
injected intraventricularly.
Lee et al. [89]
(2017)
Mice
Familial
Alzheimer’s
disease
Intracerebral
injection (Injection
into the hippocampi)
(xenogenic
MSCs—Human
MSCs)
Ferumoxytol was used to label
MSCs.
MRI and histology were used to
assess biodistribution.
Techniques were performed at 1, 7 and 14 days.
MSCs were found to remain in the injection site
up to 14 days after injection.
Wang et al.
[86] (2018)
Sprague
Dawley
rats
Glioma
(unknown
number)
Intracerebral
(MSCs were injected
contralaterally to
glioma)
(allogenic MSCs)
CM-Dil staining was used to label
MSCs, which also contained
Paclitaxel.
Confocal laser-scanning microscopy
was used to assess the distribution
of MSCs. Later histological
examinations assessed the
distribution of MSCs within the
brain.
Necropsies were performed 2 days after MSCs
injection.
MSCs were distributed in clusters in the
injection area, and were also found within the
glioma.
MSCs seem to spread within
a short period of time from
one hemisphere to another,
after intracerebral injection.
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Table 6. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Mezzanote
et al. [94]
(2017)
Mice
Healthy mice
(unknown
number)
Intracerebral
injection (brain
cortex)
MSCs were transfected with a novel
bioluminescent/near infrared
fluorescent (NIRF) fusion gene.
Fluorescence images and
bioluminescence were used to
assess the distribution of the cells.
Images were taken up to week 7 after
transplantation.
Movement of the MSCs was not assessed.
MSCs were detected for 7 weeks without a
significant drop in bioluminescent signals,
suggesting the sustained viability of hMSCs
transplanted into the cortex.
No specific biodistribution
assessment.
Da Silva et al.
[92] (2019)
Rats
Ischemic stroke
model
Intracerebral
injection
(xenogenic
MSCs—Human
MSCs).
MSCs were labeled with luciferase
and multimodal nanoparticles with
iron. In vivo bioluminescence,
near-infrared imaging and ex vivo
MRI were used to assess
biodistribution.
Biodistribution was assessed at 4 h and 6 days
after cell injection.
MSCs did not distribute. The amount of MSCs
decreased drastically from 4 h to 6 days.
Ohki et al.
[93] (2020)
Rats
Healthy model
Intracerebral
injection
(xenogenic
MSCs—Human
MSCs).
MSCs were labeled with SPIO or
USPIO. MRI and histological
examinations were performed to
assess biodistribution.
MRI images were obtained immediately and at
7- and 14-days post injection.
No MSCs demonstrated migration.
Sukhinich
et al. [53]
(2020)
Rats
Healthy model
Intracerebral and
selective
intra-arterial
(internal carotid
artery)
(xenogenic
MSCs—Human
MSCs).
MSCs were labeled with SPION and
PKH26.
MRI imaging and histology were
performed to assess biodistribution.
The distribution and migration of MSC were
analyzed by MRI from day 1 to day 15, and
histological methods on days 1, 2, 3, 7, and 15.
After intracerebral injection, MSCs moved to
corpus callosum and blood vessels.
After intraarterial injection, most MSCs were
detected in the ipsilateral hemisphere and most
of them within the blood vessels.
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Table 6. Cont.
Article
Model
Disease
(Number of
Animals)
Route of
Administration
(Source of Cells)
Cell-Marking Technique
Detection Time and Outcome
Comments
Teo et al.
[139] (2015)
Mice
Dermal
inflammation
(unknown
number)
Retro-orbital
injection.
(xenogenic
MSCs—Human
MSCs).
MSCs were labelled with specific
techniques for intravital confocal
microscopy (DiI, DiO, DiD or DiR
solution).
Later confocal microscopy was used
to assess the histologic distribution
of MSCs
Imaging was performed 2 h, 4 h and 6 h after
the MSC had been infused. When MSCs were
detected, images were taken every 5 min.
By 2 h post-infusion, arrested and
transmigrating MSC were equally distributed
within both small capillaries and larger
venules. These MSCs were in contact with
neutrophil-platelet clusters.
Platelet depletion led to significantly reduced
the preferential homing of MSC to the inflamed
Authors concluded that
MSCs transmigrate to
tissues due to the existence
of an active adhesion
mechanism.
Platelets seem to play a
crucial role in MSCs
trafficking.
Table 7. Articles regarding biodistribution of MSCs in humans.
Article
Disease (Number
of Patients)
Route of
Administration
(Source of Mscs)
Cell-Marking Technique
Detection Time and Outcome
Comments
Krueger et al.
[126] (2018)
Breast cancer (28
patients) [116]
Intravenous
(autogenic MSCs)
Flow citometry
MSCs were detected for several hours post-infusion in
peripheral blood.
MSCs are rapidly (less than 1 h) cleared from peripheral
blood after intravenous infusion
The presence of MSCs in
peripheral blood was not
detected after 1 h
post-infusion.
Cirrhosis
(4 patients) [115]
Intravenous
(autogenic MSCs)
111In-oxine labeled
mesenchymal stem cells,
evaluated with Dual head
gamma camera and SPECT
imaging techniques.
MSCs were detected at 2 h, 4 h, 6 h, 24 h, 48 h, 7th and
10th days after infusion.
Pre-48 h images showed a large majority of cells
distributed in the lungs. Later images showed a drastic
decrease in lung captation, with a higher amount of
MSCs distributed in the spleen and few in liver.
There was a clear initial
biodistribution in lungs,
which decreased after 48 h.
Spleen captation was higher
than liver captation, maybe
due to splenomegaly.
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Table 7. Cont.
Article
Disease (Number
of Patients)
Route of
Administration
(Source of Mscs)
Cell-Marking Technique
Detection Time and Outcome
Comments
Henriksson et al.
[118] (2019)
Intervertebral disc
degeneration
(4 patients)
Intralesional
(autogenic MSCs)
MSCs were labeled with iron
sucrose (Venofer®).
Histologic examinations were
performed to detect the cells.
Intravertebral discs were explanted at 8 months
(3 patients) and 28 months (1 patient) post injection.
MSCs were detected at 8 months, but not at 28 months.
Detected MSCs had differentiated into chondrocyte-like
cells.
MSCs seem to home in
intravertebral discs after
intralesional injection for
long periods of time.
Sokal et al. [117]
(2017)
Haemophilia A
(1 patient)
Intravenous
(Adult-derived human
liver stem cells)
(allogenic MSCs)
MSCs were labeled with
111In-Oxine and
biodistribution was assessed
with sequential planar
imaging (SPECT, TC).
Total body imaging was performed at 1, 4, 24, 48, 72, and
144 h postinfusion.
MSCs were initially (1 h) trapped in the lungs and liver.
At 24 h, MSCs were detected in the right ankle (where
hemarthrosis was recurrent). Up to day 6, lungs signal
decreased and liver signal increased. MSCs were also
detected in small amounts in spleen and bone marrow.
MSCs infusion seemed to
result in an improved
bleeding phenotype and was
well tolerated. Moreover, the
distribution of MSCs to the
place of bleeding suggests
possible in situ production of
factor VIII.
Sood et al. [122]
(2015)
Type 2 diabetes
mellitus
(21 patients)
Intravenous and
selective intraarterial
(superior
pancreaticoduodenal
artery and proximal
splenic artery)
(autogenic bone marrow
MSCs).
MSCs were labeled with
18-FDG.
PET-TC images were used to
assess biodistribution
Images were taken at 30 and 90 min post infusion.
In the intravenous group, MSCs distributed to lungs at
30 min with significant clearance in the delayed 90-min
image, with no distribution to pancreas. Selective
intraarterial delivery led to MSCs homing in pancreas
head (pancreaticoduodenal artery) or body (splenic
artery).
Selective intraarterial
delivery leads to selective
homing of MSCs into the
pancreas.
Lezaic et al. [119]
(2016)
Idiopathic dilated
cardiomyopathy
(35 patients)
Intracoronary infusion
(autogenic MSCs)
MSCs were labeled with
99mTc-HMPAO.
Gamma-cammera images
were taken to assess
biodistribution.
Imaging was performed 1 h and 18 h after transplantation.
At 1 h after intracoronary administration, the majority of
MSCs accumulated in the liver, spleen and bone marrow.
Accumulation of MSCs in the myocardium ranged from 0
to 1.45% of injected activity in the field of view. The
distribution of labeled stem cells in the myocardium
corresponded to the area supplied by the vessel used for
administration. At imaging 18 h post injection, the
distribution of labeled stem cells appeared unchanged,
but with decreased activity.
The retention of MSCs in the
myocardium is low after
intracoronary injection.
J. Clin. Med. 2021, 10, 2925
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Author Contributions: Conceptualization M.S.-D., S.A.-S. and A.M.-L. Search strategy: M.S.-D.,
M.I.Q.-V., R.S.d.l.T. and T.M.-V. Article review M.S.-D., T.M.-V. and A.S.-S. Expert revision: A.M.-L.
and S.A.-S. Manuscript preparation M.S.-D., T.M.-V., A.S.-S., M.I.Q.-V. and R.S.d.l.T. All authors have
read and agreed to the published version of the manuscript.
Funding: This research has received competitive funding in the call for grants for the financing of
Research, Development and Innovation in Biomedicine and Health Sciences in Andalusia, for the
year 2019 (PIGE-0247-2019; PIGE-0242-2019).
Institutional Review Board Statement: Not applicable because no humans or animals were present
in a systematic review.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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